#!/usr/bin/env python """ fitpack (dierckx in netlib) --- A Python-C wrapper to FITPACK (by P. Dierckx). FITPACK is a collection of FORTRAN programs for curve and surface fitting with splines and tensor product splines. See http://www.cs.kuleuven.ac.be/cwis/research/nalag/research/topics/fitpack.html or http://www.netlib.org/dierckx/index.html Copyright 2002 Pearu Peterson all rights reserved, Pearu Peterson Permission to use, modify, and distribute this software is given under the terms of the SciPy (BSD style) license. See LICENSE.txt that came with this distribution for specifics. NO WARRANTY IS EXPRESSED OR IMPLIED. USE AT YOUR OWN RISK. Pearu Peterson Running test programs: $ python fitpack.py 1 3 # run test programs 1, and 3 $ python fitpack.py # run all available test programs TODO: Make interfaces to the following fitpack functions: For univariate splines: cocosp, concon, fourco, insert For bivariate splines: profil, regrid, parsur, surev """ __all__ = ['splrep', 'splprep', 'splev', 'splint', 'sproot', 'spalde', 'bisplrep', 'bisplev', 'insert'] __version__ = "$Revision$"[10:-1] import _fitpack from numpy import atleast_1d, array, ones, zeros, sqrt, ravel, transpose, \ dot, sin, cos, pi, arange, empty, int32 myasarray = atleast_1d # Try to replace _fitpack interface with # f2py-generated version import dfitpack _iermess = {0:["""\ The spline has a residual sum of squares fp such that abs(fp-s)/s<=0.001""",None], -1:["""\ The spline is an interpolating spline (fp=0)""",None], -2:["""\ The spline is weighted least-squares polynomial of degree k. fp gives the upper bound fp0 for the smoothing factor s""",None], 1:["""\ The required storage space exceeds the available storage space. Probable causes: data (x,y) size is too small or smoothing parameter s is too small (fp>s).""",ValueError], 2:["""\ A theoretically impossible results when finding a smoothin spline with fp = s. Probably causes: s too small. (abs(fp-s)/s>0.001)""",ValueError], 3:["""\ The maximal number of iterations (20) allowed for finding smoothing spline with fp=s has been reached. Probably causes: s too small. (abs(fp-s)/s>0.001)""",ValueError], 10:["""\ Error on input data""",ValueError], 'unknown':["""\ An error occurred""",TypeError]} _iermess2 = {0:["""\ The spline has a residual sum of squares fp such that abs(fp-s)/s<=0.001""",None], -1:["""\ The spline is an interpolating spline (fp=0)""",None], -2:["""\ The spline is weighted least-squares polynomial of degree kx and ky. fp gives the upper bound fp0 for the smoothing factor s""",None], -3:["""\ Warning. The coefficients of the spline have been computed as the minimal norm least-squares solution of a rank deficient system.""",None], 1:["""\ The required storage space exceeds the available storage space. Probably causes: nxest or nyest too small or s is too small. (fp>s)""",ValueError], 2:["""\ A theoretically impossible results when finding a smoothin spline with fp = s. Probably causes: s too small or badly chosen eps. (abs(fp-s)/s>0.001)""",ValueError], 3:["""\ The maximal number of iterations (20) allowed for finding smoothing spline with fp=s has been reached. Probably causes: s too small. (abs(fp-s)/s>0.001)""",ValueError], 4:["""\ No more knots can be added because the number of B-spline coefficients already exceeds the number of data points m. Probably causes: either s or m too small. (fp>s)""",ValueError], 5:["""\ No more knots can be added because the additional knot would coincide with an old one. Probably cause: s too small or too large a weight to an inaccurate data point. (fp>s)""",ValueError], 10:["""\ Error on input data""",ValueError], 11:["""\ rwrk2 too small, i.e. there is not enough workspace for computing the minimal least-squares solution of a rank deficient system of linear equations.""",ValueError], 'unknown':["""\ An error occurred""",TypeError]} _parcur_cache = {'t': array([],float), 'wrk': array([],float), 'iwrk':array([],int32), 'u': array([],float),'ub':0,'ue':1} def splprep(x,w=None,u=None,ub=None,ue=None,k=3,task=0,s=None,t=None, full_output=0,nest=None,per=0,quiet=1): """ Find the B-spline representation of an N-dimensional curve. Given a list of N rank-1 arrays, x, which represent a curve in N-dimensional space parametrized by u, find a smooth approximating spline curve g(u). Uses the FORTRAN routine parcur from FITPACK. Parameters ---------- x : array_like A list of sample vector arrays representing the curve. u : array_like, optional An array of parameter values. If not given, these values are calculated automatically as ``M = len(x[0])``: v[0] = 0 v[i] = v[i-1] + distance(x[i],x[i-1]) u[i] = v[i] / v[M-1] ub, ue : int, optional The end-points of the parameters interval. Defaults to u[0] and u[-1]. k : int, optional Degree of the spline. Cubic splines are recommended. Even values of `k` should be avoided especially with a small s-value. ``1 <= k <= 5``, default is 3. task : int, optional If task==0 (default), find t and c for a given smoothing factor, s. If task==1, find t and c for another value of the smoothing factor, s. There must have been a previous call with task=0 or task=1 for the same set of data. If task=-1 find the weighted least square spline for a given set of knots, t. s : float, optional A smoothing condition. The amount of smoothness is determined by satisfying the conditions: ``sum((w * (y - g))**2,axis=0) <= s``, where g(x) is the smoothed interpolation of (x,y). The user can use `s` to control the trade-off between closeness and smoothness of fit. Larger `s` means more smoothing while smaller values of `s` indicate less smoothing. Recommended values of `s` depend on the weights, w. If the weights represent the inverse of the standard-deviation of y, then a good `s` value should be found in the range ``(m-sqrt(2*m),m+sqrt(2*m))``, where m is the number of data points in x, y, and w. t : int, optional The knots needed for task=-1. full_output : int, optional If non-zero, then return optional outputs. nest : int, optional An over-estimate of the total number of knots of the spline to help in determining the storage space. By default nest=m/2. Always large enough is nest=m+k+1. per : int, optional If non-zero, data points are considered periodic with period x[m-1] - x[0] and a smooth periodic spline approximation is returned. Values of y[m-1] and w[m-1] are not used. quiet : int, optional Non-zero to suppress messages. Returns ------- tck : tuple A tuple (t,c,k) containing the vector of knots, the B-spline coefficients, and the degree of the spline. u : array An array of the values of the parameter. fp : float The weighted sum of squared residuals of the spline approximation. ier : int An integer flag about splrep success. Success is indicated if ier<=0. If ier in [1,2,3] an error occurred but was not raised. Otherwise an error is raised. msg : str A message corresponding to the integer flag, ier. See Also -------- splrep, splev, sproot, spalde, splint, bisplrep, bisplev UnivariateSpline, BivariateSpline Notes ----- See `splev` for evaluation of the spline and its derivatives. References ---------- .. [1] P. Dierckx, "Algorithms for smoothing data with periodic and parametric splines, Computer Graphics and Image Processing", 20 (1982) 171-184. .. [2] P. Dierckx, "Algorithms for smoothing data with periodic and parametric splines", report tw55, Dept. Computer Science, K.U.Leuven, 1981. .. [3] P. Dierckx, "Curve and surface fitting with splines", Monographs on Numerical Analysis, Oxford University Press, 1993. """ if task<=0: _parcur_cache = {'t': array([],float), 'wrk': array([],float), 'iwrk':array([],int32),'u': array([],float), 'ub':0,'ue':1} x=myasarray(x) idim,m=x.shape if per: for i in range(idim): if x[i][0]!=x[i][-1]: if quiet<2:print 'Warning: Setting x[%d][%d]=x[%d][0]'%(i,m,i) x[i][-1]=x[i][0] if not 0 < idim < 11: raise TypeError('0 < idim < 11 must hold') if w is None: w = ones(m, float) else: w = myasarray(w) ipar = (u is not None) if ipar: _parcur_cache['u']=u if ub is None: _parcur_cache['ub']=u[0] else: _parcur_cache['ub']=ub if ue is None: _parcur_cache['ue']=u[-1] else: _parcur_cache['ue']=ue else: _parcur_cache['u']=zeros(m,float) if not (1 <= k <= 5): raise TypeError('1 <= k= %d <=5 must hold' % k) if not (-1 <= task <=1): raise TypeError('task must be -1, 0 or 1') if (not len(w)==m) or (ipar==1 and (not len(u)==m)): raise TypeError('Mismatch of input dimensions') if s is None: s=m-sqrt(2*m) if t is None and task == -1: raise TypeError('Knots must be given for task=-1') if t is not None: _parcur_cache['t']=myasarray(t) n=len(_parcur_cache['t']) if task==-1 and n<2*k+2: raise TypeError('There must be at least 2*k+2 knots for task=-1') if m <= k: raise TypeError('m > k must hold') if nest is None: nest=m+2*k if (task>=0 and s==0) or (nest<0): if per: nest=m+2*k else: nest=m+k+1 nest=max(nest,2*k+3) u=_parcur_cache['u'] ub=_parcur_cache['ub'] ue=_parcur_cache['ue'] t=_parcur_cache['t'] wrk=_parcur_cache['wrk'] iwrk=_parcur_cache['iwrk'] t,c,o=_fitpack._parcur(ravel(transpose(x)),w,u,ub,ue,k,task,ipar,s,t, nest,wrk,iwrk,per) _parcur_cache['u']=o['u'] _parcur_cache['ub']=o['ub'] _parcur_cache['ue']=o['ue'] _parcur_cache['t']=t _parcur_cache['wrk']=o['wrk'] _parcur_cache['iwrk']=o['iwrk'] ier,fp,n=o['ier'],o['fp'],len(t) u=o['u'] c.shape=idim,n-k-1 tcku = [t,list(c),k],u if ier<=0 and not quiet: print _iermess[ier][0] print "\tk=%d n=%d m=%d fp=%f s=%f"%(k,len(t),m,fp,s) if ier>0 and not full_output: if ier in [1,2,3]: print "Warning: "+_iermess[ier][0] else: try: raise _iermess[ier][1](_iermess[ier][0]) except KeyError: raise _iermess['unknown'][1](_iermess['unknown'][0]) if full_output: try: return tcku,fp,ier,_iermess[ier][0] except KeyError: return tcku,fp,ier,_iermess['unknown'][0] else: return tcku _curfit_cache = {'t': array([],float), 'wrk': array([],float), 'iwrk':array([],int32)} def splrep(x,y,w=None,xb=None,xe=None,k=3,task=0,s=None,t=None, full_output=0,per=0,quiet=1): """ Find the B-spline representation of 1-D curve. Given the set of data points (x[i], y[i]) determine a smooth spline approximation of degree k on the interval xb <= x <= xe. The coefficients, c, and the knot points, t, are returned. Uses the FORTRAN routine curfit from FITPACK. Parameters ---------- x, y : array_like The data points defining a curve y = f(x). w : array_like Strictly positive rank-1 array of weights the same length as x and y. The weights are used in computing the weighted least-squares spline fit. If the errors in the y values have standard-deviation given by the vector d, then w should be 1/d. Default is ones(len(x)). xb, xe : float The interval to fit. If None, these default to x[0] and x[-1] respectively. k : int The order of the spline fit. It is recommended to use cubic splines. Even order splines should be avoided especially with small s values. 1 <= k <= 5 task : {1, 0, -1} If task==0 find t and c for a given smoothing factor, s. If task==1 find t and c for another value of the smoothing factor, s. There must have been a previous call with task=0 or task=1 for the same set of data (t will be stored an used internally) If task=-1 find the weighted least square spline for a given set of knots, t. These should be interior knots as knots on the ends will be added automatically. s : float A smoothing condition. The amount of smoothness is determined by satisfying the conditions: sum((w * (y - g))**2,axis=0) <= s where g(x) is the smoothed interpolation of (x,y). The user can use s to control the tradeoff between closeness and smoothness of fit. Larger s means more smoothing while smaller values of s indicate less smoothing. Recommended values of s depend on the weights, w. If the weights represent the inverse of the standard-deviation of y, then a good s value should be found in the range (m-sqrt(2*m),m+sqrt(2*m)) where m is the number of datapoints in x, y, and w. default : s=m-sqrt(2*m) if weights are supplied. s = 0.0 (interpolating) if no weights are supplied. t : int The knots needed for task=-1. If given then task is automatically set to -1. full_output : bool If non-zero, then return optional outputs. per : bool If non-zero, data points are considered periodic with period x[m-1] - x[0] and a smooth periodic spline approximation is returned. Values of y[m-1] and w[m-1] are not used. quiet : bool Non-zero to suppress messages. Returns ------- tck : tuple (t,c,k) a tuple containing the vector of knots, the B-spline coefficients, and the degree of the spline. fp : array, optional The weighted sum of squared residuals of the spline approximation. ier : int, optional An integer flag about splrep success. Success is indicated if ier<=0. If ier in [1,2,3] an error occurred but was not raised. Otherwise an error is raised. msg : str, optional A message corresponding to the integer flag, ier. Notes ----- See splev for evaluation of the spline and its derivatives. See Also -------- UnivariateSpline, BivariateSpline splprep, splev, sproot, spalde, splint bisplrep, bisplev References ---------- Based on algorithms described in [1], [2], [3], and [4]: .. [1] P. Dierckx, "An algorithm for smoothing, differentiation and integration of experimental data using spline functions", J.Comp.Appl.Maths 1 (1975) 165-184. .. [2] P. Dierckx, "A fast algorithm for smoothing data on a rectangular grid while using spline functions", SIAM J.Numer.Anal. 19 (1982) 1286-1304. .. [3] P. Dierckx, "An improved algorithm for curve fitting with spline functions", report tw54, Dept. Computer Science,K.U. Leuven, 1981. .. [4] P. Dierckx, "Curve and surface fitting with splines", Monographs on Numerical Analysis, Oxford University Press, 1993. Examples -------- >>> x = linspace(0, 10, 10) >>> y = sin(x) >>> tck = splrep(x, y) >>> x2 = linspace(0, 10, 200) >>> y2 = splev(x2, tck) >>> plot(x, y, 'o', x2, y2) """ if task<=0: _curfit_cache = {} x,y=map(myasarray,[x,y]) m=len(x) if w is None: w=ones(m,float) if s is None: s = 0.0 else: w=myasarray(w) if s is None: s = m-sqrt(2*m) if not len(w) == m: raise TypeError('len(w)=%d is not equal to m=%d' % (len(w),m)) if (m != len(y)) or (m != len(w)): raise TypeError('Lengths of the first three arguments (x,y,w) must be equal') if not (1 <= k <= 5): raise TypeError('Given degree of the spline (k=%d) is not supported. (1<=k<=5)' % k) if m <= k: raise TypeError('m > k must hold') if xb is None: xb=x[0] if xe is None: xe=x[-1] if not (-1 <= task <= 1): raise TypeError('task must be -1, 0 or 1') if t is not None: task = -1 if task == -1: if t is None: raise TypeError('Knots must be given for task=-1') numknots = len(t) _curfit_cache['t'] = empty((numknots + 2*k+2,),float) _curfit_cache['t'][k+1:-k-1] = t nest = len(_curfit_cache['t']) elif task == 0: if per: nest = max(m+2*k,2*k+3) else: nest = max(m+k+1,2*k+3) t = empty((nest,),float) _curfit_cache['t'] = t if task <= 0: if per: _curfit_cache['wrk'] = empty((m*(k+1)+nest*(8+5*k),),float) else: _curfit_cache['wrk'] = empty((m*(k+1)+nest*(7+3*k),),float) _curfit_cache['iwrk'] = empty((nest,),int32) try: t=_curfit_cache['t'] wrk=_curfit_cache['wrk'] iwrk=_curfit_cache['iwrk'] except KeyError: raise TypeError("must call with task=1 only after" " call with task=0,-1") if not per: n,c,fp,ier = dfitpack.curfit(task, x, y, w, t, wrk, iwrk, xb, xe, k, s) else: n,c,fp,ier = dfitpack.percur(task, x, y, w, t, wrk, iwrk, k, s) tck = (t[:n],c[:n],k) if ier<=0 and not quiet: print _iermess[ier][0] print "\tk=%d n=%d m=%d fp=%f s=%f"%(k,len(t),m,fp,s) if ier>0 and not full_output: if ier in [1,2,3]: print "Warning: "+_iermess[ier][0] else: try: raise _iermess[ier][1](_iermess[ier][0]) except KeyError: raise _iermess['unknown'][1](_iermess['unknown'][0]) if full_output: try: return tck,fp,ier,_iermess[ier][0] except KeyError: return tck,fp,ier,_iermess['unknown'][0] else: return tck def _ntlist(l): # return non-trivial list return l #if len(l)>1: return l #return l[0] def splev(x, tck, der=0, ext=0): """ Evaluate a B-spline or its derivatives. Given the knots and coefficients of a B-spline representation, evaluate the value of the smoothing polynomial and its derivatives. This is a wrapper around the FORTRAN routines splev and splder of FITPACK. Parameters ---------- x : array_like A 1-D array of points at which to return the value of the smoothed spline or its derivatives. If `tck` was returned from `splprep`, then the parameter values, u should be given. tck : tuple A sequence of length 3 returned by `splrep` or `splprep` containing the knots, coefficients, and degree of the spline. der : int The order of derivative of the spline to compute (must be less than or equal to k). ext : int Controls the value returned for elements of ``x`` not in the interval defined by the knot sequence. * if ext=0, return the extrapolated value. * if ext=1, return 0 * if ext=2, raise a ValueError The default value is 0. Returns ------- y : ndarray or list of ndarrays An array of values representing the spline function evaluated at the points in ``x``. If `tck` was returned from splrep, then this is a list of arrays representing the curve in N-dimensional space. See Also -------- splprep, splrep, sproot, spalde, splint bisplrep, bisplev References ---------- .. [1] C. de Boor, "On calculating with b-splines", J. Approximation Theory, 6, p.50-62, 1972. .. [2] M.G. Cox, "The numerical evaluation of b-splines", J. Inst. Maths Applics, 10, p.134-149, 1972. .. [3] P. Dierckx, "Curve and surface fitting with splines", Monographs on Numerical Analysis, Oxford University Press, 1993. """ t,c,k = tck try: c[0][0] parametric = True except: parametric = False if parametric: return map(lambda c, x=x, t=t, k=k, der=der : splev(x, [t,c,k], der), c) else: if not (0 <= der <= k): raise ValueError("0<=der=%d<=k=%d must hold"%(der,k)) if not ext in (0,1,2): raise ValueError("ext not in (0, 1, 2)") x = myasarray(x) y, ier =_fitpack._spl_(x, der, t, c, k, ext) if ier == 10: raise ValueError("Invalid input data") if ier == 1: raise ValueError("Found x value not in the domain") if ier: raise TypeError("An error occurred") if len(y) > 1: return y return y[0] def splint(a,b,tck,full_output=0): """ Evaluate the definite integral of a B-spline. Given the knots and coefficients of a B-spline, evaluate the definite integral of the smoothing polynomial between two given points. Parameters ---------- a, b : float The end-points of the integration interval. tck : tuple A tuple (t,c,k) containing the vector of knots, the B-spline coefficients, and the degree of the spline (see `splev`). full_output : int, optional Non-zero to return optional output. Returns ------- integral : float The resulting integral. wrk : ndarray An array containing the integrals of the normalized B-splines defined on the set of knots. See Also -------- splprep, splrep, sproot, spalde, splev bisplrep, bisplev UnivariateSpline, BivariateSpline References ---------- .. [1] P.W. Gaffney, The calculation of indefinite integrals of b-splines", J. Inst. Maths Applics, 17, p.37-41, 1976. .. [2] P. Dierckx, "Curve and surface fitting with splines", Monographs on Numerical Analysis, Oxford University Press, 1993. """ t,c,k=tck try: c[0][0] parametric = True except: parametric = False if parametric: return _ntlist(map(lambda c,a=a,b=b,t=t,k=k:splint(a,b,[t,c,k]),c)) else: aint,wrk=_fitpack._splint(t,c,k,a,b) if full_output: return aint,wrk else: return aint def sproot(tck,mest=10): """ Find the roots of a cubic B-spline. Given the knots (>=8) and coefficients of a cubic B-spline return the roots of the spline. Parameters ---------- tck : tuple A tuple (t,c,k) containing the vector of knots, the B-spline coefficients, and the degree of the spline. The number of knots must be >= 8. The knots must be a montonically increasing sequence. mest : int An estimate of the number of zeros (Default is 10). Returns ------- zeros : ndarray An array giving the roots of the spline. See also -------- splprep, splrep, splint, spalde, splev bisplrep, bisplev UnivariateSpline, BivariateSpline References ---------- .. [1] C. de Boor, "On calculating with b-splines", J. Approximation Theory, 6, p.50-62, 1972. .. [2] M.G. Cox, "The numerical evaluation of b-splines", J. Inst. Maths Applics, 10, p.134-149, 1972. .. [3] P. Dierckx, "Curve and surface fitting with splines", Monographs on Numerical Analysis, Oxford University Press, 1993. """ t,c,k=tck if k==4: t=t[1:-1] if k==5: t=t[2:-2] try: c[0][0] parametric = True except: parametric = False if parametric: return _ntlist(map(lambda c,t=t,k=k,mest=mest:sproot([t,c,k],mest),c)) else: if len(t)<8: raise TypeError("The number of knots %d>=8" % len(t)) z,ier=_fitpack._sproot(t,c,k,mest) if ier==10: raise TypeError("Invalid input data. t1<=..<=t41: return map(lambda x,tck=tck:spalde(x,tck),x) d,ier=_fitpack._spalde(t,c,k,x[0]) if ier==0: return d if ier==10: raise TypeError("Invalid input data. t(k)<=x<=t(n-k+1) must hold.") raise TypeError("Unknown error") #def _curfit(x,y,w=None,xb=None,xe=None,k=3,task=0,s=None,t=None, # full_output=0,nest=None,per=0,quiet=1): _surfit_cache = {'tx': array([],float),'ty': array([],float), 'wrk': array([],float), 'iwrk':array([],int32)} def bisplrep(x,y,z,w=None,xb=None,xe=None,yb=None,ye=None,kx=3,ky=3,task=0, s=None,eps=1e-16,tx=None,ty=None,full_output=0, nxest=None,nyest=None,quiet=1): """ Find a bivariate B-spline representation of a surface. Given a set of data points (x[i], y[i], z[i]) representing a surface z=f(x,y), compute a B-spline representation of the surface. Based on the routine SURFIT from FITPACK. Parameters ---------- x, y, z : ndarray Rank-1 arrays of data points. w : ndarray, optional Rank-1 array of weights. By default ``w=np.ones(len(x))``. xb, xe : float, optional End points of approximation interval in `x`. By default ``xb = x.min(), xe=x.max()``. yb, ye : float, optional End points of approximation interval in `y`. By default ``yb=y.min(), ye = y.max()``. kx, ky : int, optional The degrees of the spline (1 <= kx, ky <= 5). Third order (kx=ky=3) is recommended. task : int, optional If task=0, find knots in x and y and coefficients for a given smoothing factor, s. If task=1, find knots and coefficients for another value of the smoothing factor, s. bisplrep must have been previously called with task=0 or task=1. If task=-1, find coefficients for a given set of knots tx, ty. s : float, optional A non-negative smoothing factor. If weights correspond to the inverse of the standard-deviation of the errors in z, then a good s-value should be found in the range ``(m-sqrt(2*m),m+sqrt(2*m))`` where m=len(x). eps : float, optional A threshold for determining the effective rank of an over-determined linear system of equations (0 < eps < 1). `eps` is not likely to need changing. tx, ty : ndarray, optional Rank-1 arrays of the knots of the spline for task=-1 full_output : int, optional Non-zero to return optional outputs. nxest, nyest : int, optional Over-estimates of the total number of knots. If None then ``nxest = max(kx+sqrt(m/2),2*kx+3)``, ``nyest = max(ky+sqrt(m/2),2*ky+3)``. quiet : int, optional Non-zero to suppress printing of messages. Returns ------- tck : array_like A list [tx, ty, c, kx, ky] containing the knots (tx, ty) and coefficients (c) of the bivariate B-spline representation of the surface along with the degree of the spline. fp : ndarray The weighted sum of squared residuals of the spline approximation. ier : int An integer flag about splrep success. Success is indicated if ier<=0. If ier in [1,2,3] an error occurred but was not raised. Otherwise an error is raised. msg : str A message corresponding to the integer flag, ier. See Also -------- splprep, splrep, splint, sproot, splev UnivariateSpline, BivariateSpline Notes ----- See `bisplev` to evaluate the value of the B-spline given its tck representation. References ---------- .. [1] Dierckx P.:An algorithm for surface fitting with spline functions Ima J. Numer. Anal. 1 (1981) 267-283. .. [2] Dierckx P.:An algorithm for surface fitting with spline functions report tw50, Dept. Computer Science,K.U.Leuven, 1980. .. [3] Dierckx P.:Curve and surface fitting with splines, Monographs on Numerical Analysis, Oxford University Press, 1993. """ x,y,z=map(myasarray,[x,y,z]) x,y,z=map(ravel,[x,y,z]) # ensure 1-d arrays. m=len(x) if not (m==len(y)==len(z)): raise TypeError('len(x)==len(y)==len(z) must hold.') if w is None: w=ones(m,float) else: w=myasarray(w) if not len(w) == m: raise TypeError('len(w)=%d is not equal to m=%d' % (len(w), m)) if xb is None: xb=x.min() if xe is None: xe=x.max() if yb is None: yb=y.min() if ye is None: ye=y.max() if not (-1<=task<=1): raise TypeError('task must be -1, 0 or 1') if s is None: s=m-sqrt(2*m) if tx is None and task==-1: raise TypeError('Knots_x must be given for task=-1') if tx is not None: _surfit_cache['tx']=myasarray(tx) nx=len(_surfit_cache['tx']) if ty is None and task==-1: raise TypeError('Knots_y must be given for task=-1') if ty is not None: _surfit_cache['ty']=myasarray(ty) ny=len(_surfit_cache['ty']) if task==-1 and nx<2*kx+2: raise TypeError('There must be at least 2*kx+2 knots_x for task=-1') if task==-1 and ny<2*ky+2: raise TypeError('There must be at least 2*ky+2 knots_x for task=-1') if not ((1<=kx<=5) and (1<=ky<=5)): raise TypeError('Given degree of the spline (kx,ky=%d,%d) is not supported. (1<=k<=5)' % (kx,ky)) if m<(kx+1)*(ky+1): raise TypeError('m >= (kx+1)(ky+1) must hold') if nxest is None: nxest=int(kx+sqrt(m/2)) if nyest is None: nyest=int(ky+sqrt(m/2)) nxest,nyest=max(nxest,2*kx+3),max(nyest,2*ky+3) if task>=0 and s==0: nxest=int(kx+sqrt(3*m)) nyest=int(ky+sqrt(3*m)) if task==-1: _surfit_cache['tx']=myasarray(tx) _surfit_cache['ty']=myasarray(ty) tx,ty=_surfit_cache['tx'],_surfit_cache['ty'] wrk=_surfit_cache['wrk'] iwrk=_surfit_cache['iwrk'] u,v,km,ne=nxest-kx-1,nyest-ky-1,max(kx,ky)+1,max(nxest,nyest) bx,by=kx*v+ky+1,ky*u+kx+1 b1,b2=bx,bx+v-ky if bx>by: b1,b2=by,by+u-kx try: lwrk1=int32(u*v*(2+b1+b2)+2*(u+v+km*(m+ne)+ne-kx-ky)+b2+1) lwrk2=int32(u*v*(b2+1)+b2) except OverflowError: raise OverflowError("Too many data points to interpolate") tx,ty,c,o = _fitpack._surfit(x,y,z,w,xb,xe,yb,ye,kx,ky,task,s,eps, tx,ty,nxest,nyest,wrk,lwrk1,lwrk2) _curfit_cache['tx']=tx _curfit_cache['ty']=ty _curfit_cache['wrk']=o['wrk'] ier,fp=o['ier'],o['fp'] tck=[tx,ty,c,kx,ky] ierm=min(11,max(-3,ier)) if ierm<=0 and not quiet: print _iermess2[ierm][0] print "\tkx,ky=%d,%d nx,ny=%d,%d m=%d fp=%f s=%f"%(kx,ky,len(tx), len(ty),m,fp,s) if ierm>0 and not full_output: if ier in [1,2,3,4,5]: print "Warning: "+_iermess2[ierm][0] print "\tkx,ky=%d,%d nx,ny=%d,%d m=%d fp=%f s=%f"%(kx,ky,len(tx), len(ty),m,fp,s) else: try: raise _iermess2[ierm][1](_iermess2[ierm][0]) except KeyError: raise _iermess2['unknown'][1](_iermess2['unknown'][0]) if full_output: try: return tck,fp,ier,_iermess2[ierm][0] except KeyError: return tck,fp,ier,_iermess2['unknown'][0] else: return tck def bisplev(x,y,tck,dx=0,dy=0): """ Evaluate a bivariate B-spline and its derivatives. Return a rank-2 array of spline function values (or spline derivative values) at points given by the cross-product of the rank-1 arrays x and y. In special cases, return an array or just a float if either x or y or both are floats. Based on BISPEV from FITPACK. Parameters ---------- x, y : ndarray Rank-1 arrays specifying the domain over which to evaluate the spline or its derivative. tck : tuple A sequence of length 5 returned by `bisplrep` containing the knot locations, the coefficients, and the degree of the spline: [tx, ty, c, kx, ky]. dx, dy : int, optional The orders of the partial derivatives in `x` and `y` respectively. Returns ------- vals : ndarray The B-spline or its derivative evaluated over the set formed by the cross-product of `x` and `y`. See Also -------- splprep, splrep, splint, sproot, splev UnivariateSpline, BivariateSpline Notes ----- See `bisplrep` to generate the `tck` representation. References ---------- .. [1] Dierckx P. : An algorithm for surface fitting with spline functions Ima J. Numer. Anal. 1 (1981) 267-283. .. [2] Dierckx P. : An algorithm for surface fitting with spline functions report tw50, Dept. Computer Science,K.U.Leuven, 1980. .. [3] Dierckx P. : Curve and surface fitting with splines, Monographs on Numerical Analysis, Oxford University Press, 1993. """ tx,ty,c,kx,ky=tck if not (0<=dx1: return z if len(z[0])>1: return z[0] return z[0][0] def dblint(xa,xb,ya,yb,tck): """Evaluate the integral of a spline over area [xa,xb] x [ya,yb]. Parameters ---------- xa, xb : float The end-points of the x integration interval. ya, yb : float The end-points of the y integration interval. tck : list [tx, ty, c, kx, ky] A sequence of length 5 returned by bisplrep containing the knot locations tx, ty, the coefficients c, and the degrees kx, ky of the spline. Returns ------- integ : float The value of the resulting integral. """ tx,ty,c,kx,ky=tck return dfitpack.dblint(tx,ty,c,kx,ky,xb,xe,yb,ye) def insert(x,tck,m=1,per=0): """ Insert knots into a B-spline. Given the knots and coefficients of a B-spline representation, create a new B-spline with a knot inserted m times at point x. This is a wrapper around the FORTRAN routine insert of FITPACK. Parameters ---------- x (u) : array_like A 1-D point at which to insert a new knot(s). If `tck` was returned from `splprep`, then the parameter values, u should be given. tck : tuple A tuple (t,c,k) returned by `splrep` or `splprep` containing the vector of knots, the B-spline coefficients, and the degree of the spline. m : int, optional The number of times to insert the given knot (its multiplicity). Default is 1. per : int, optional If non-zero, input spline is considered periodic. Returns ------- tck : tuple A tuple (t,c,k) containing the vector of knots, the B-spline coefficients, and the degree of the new spline. ``t(k+1) <= x <= t(n-k)``, where k is the degree of the spline. In case of a periodic spline (`per` != 0) there must be either at least k interior knots t(j) satisfying ``t(k+1)0: runtest=map(int,sys.argv[1:]) put=sys.stdout.write def norm2(x): return dot(transpose(x),x) def f1(x,d=0): if d is None: return "sin" if x is None: return "sin(x)" if d%4 == 0: return sin(x) if d%4 == 1: return cos(x) if d%4 == 2: return -sin(x) if d%4 == 3: return -cos(x) def f2(x,y=0,dx=0,dy=0): if x is None: return "sin(x+y)" d=dx+dy if d%4 == 0: return sin(x+y) if d%4 == 1: return cos(x+y) if d%4 == 2: return -sin(x+y) if d%4 == 3: return -cos(x+y) def test1(f=f1,per=0,s=0,a=0,b=2*pi,N=20,at=0,xb=None,xe=None): if xb is None: xb=a if xe is None: xe=b x=a+(b-a)*arange(N+1,dtype=float)/float(N) # nodes x1=a+(b-a)*arange(1,N,dtype=float)/float(N-1) # middle points of the nodes v,v1=f(x),f(x1) nk=[] for k in range(1,6): tck=splrep(x,v,s=s,per=per,k=k,xe=xe) if at:t=tck[0][k:-k] else: t=x1 nd=[] for d in range(k+1): nd.append(norm2(f(t,d)-splev(t,tck,d))) nk.append(nd) print "\nf = %s s=S_k(x;t,c) x in [%s, %s] > [%s, %s]"%(f(None), `round(xb,3)`,`round(xe,3)`, `round(a,3)`,`round(b,3)`) if at: str="at knots" else: str="at the middle of nodes" print " per=%d s=%s Evaluation %s"%(per,`s`,str) print " k : |f-s|^2 |f'-s'| |f''-.. |f'''-. |f''''- |f'''''" k=1 for l in nk: put(' %d : '%k) for r in l: put(' %.1e'%r) put('\n') k=k+1 def test2(f=f1,per=0,s=0,a=0,b=2*pi,N=20,xb=None,xe=None, ia=0,ib=2*pi,dx=0.2*pi): if xb is None: xb=a if xe is None: xe=b x=a+(b-a)*arange(N+1,dtype=float)/float(N) # nodes v=f(x) nk=[] for k in range(1,6): tck=splrep(x,v,s=s,per=per,k=k,xe=xe) nk.append([splint(ia,ib,tck),spalde(dx,tck)]) print "\nf = %s s=S_k(x;t,c) x in [%s, %s] > [%s, %s]"%(f(None), `round(xb,3)`,`round(xe,3)`, `round(a,3)`,`round(b,3)`) print " per=%d s=%s N=%d [a, b] = [%s, %s] dx=%s"%(per,`s`,N,`round(ia,3)`,`round(ib,3)`,`round(dx,3)`) print " k : int(s,[a,b]) Int.Error Rel. error of s^(d)(dx) d = 0, .., k" k=1 for r in nk: if r[0]<0: sr='-' else: sr=' ' put(" %d %s%.8f %.1e "%(k,sr,abs(r[0]), abs(r[0]-(f(ib,-1)-f(ia,-1))))) d=0 for dr in r[1]: put(" %.1e "%(abs(1-dr/f(dx,d)))) d=d+1 put("\n") k=k+1 def test3(f=f1,per=0,s=0,a=0,b=2*pi,N=20,xb=None,xe=None, ia=0,ib=2*pi,dx=0.2*pi): if xb is None: xb=a if xe is None: xe=b x=a+(b-a)*arange(N+1,dtype=float)/float(N) # nodes v=f(x) nk=[] print " k : Roots of s(x) approx %s x in [%s,%s]:"%\ (f(None),`round(a,3)`,`round(b,3)`) for k in range(1,6): tck=splrep(x,v,s=s,per=per,k=k,xe=xe) print ' %d : %s'%(k,`sproot(tck).tolist()`) def test4(f=f1,per=0,s=0,a=0,b=2*pi,N=20,xb=None,xe=None, ia=0,ib=2*pi,dx=0.2*pi): if xb is None: xb=a if xe is None: xe=b x=a+(b-a)*arange(N+1,dtype=float)/float(N) # nodes x1=a+(b-a)*arange(1,N,dtype=float)/float(N-1) # middle points of the nodes v,v1=f(x),f(x1) nk=[] print " u = %s N = %d"%(`round(dx,3)`,N) print " k : [x(u), %s(x(u))] Error of splprep Error of splrep "%(f(0,None)) for k in range(1,6): tckp,u=splprep([x,v],s=s,per=per,k=k,nest=-1) tck=splrep(x,v,s=s,per=per,k=k) uv=splev(dx,tckp) print " %d : %s %.1e %.1e"%\ (k,`map(lambda x:round(x,3),uv)`, abs(uv[1]-f(uv[0])), abs(splev(uv[0],tck)-f(uv[0]))) print "Derivatives of parametric cubic spline at u (first function):" k=3 tckp,u=splprep([x,v],s=s,per=per,k=k,nest=-1) for d in range(1,k+1): uv=splev(dx,tckp,d) put(" %s "%(`uv[0]`)) print def makepairs(x,y): x,y=map(myasarray,[x,y]) xy=array(map(lambda x,y:map(None,len(y)*[x],y),x,len(x)*[y])) sh=xy.shape xy.shape=sh[0]*sh[1],sh[2] return transpose(xy) def test5(f=f2,kx=3,ky=3,xb=0,xe=2*pi,yb=0,ye=2*pi,Nx=20,Ny=20,s=0): x=xb+(xe-xb)*arange(Nx+1,dtype=float)/float(Nx) y=yb+(ye-yb)*arange(Ny+1,dtype=float)/float(Ny) xy=makepairs(x,y) tck=bisplrep(xy[0],xy[1],f(xy[0],xy[1]),s=s,kx=kx,ky=ky) tt=[tck[0][kx:-kx],tck[1][ky:-ky]] t2=makepairs(tt[0],tt[1]) v1=bisplev(tt[0],tt[1],tck) v2=f2(t2[0],t2[1]) v2.shape=len(tt[0]),len(tt[1]) print norm2(ravel(v1-v2)) if 1 in runtest: print """\ ****************************************** \tTests of splrep and splev ******************************************""" test1(s=1e-6) test1() test1(at=1) test1(per=1) test1(per=1,at=1) test1(b=1.5*pi) test1(b=1.5*pi,xe=2*pi,per=1,s=1e-1) if 2 in runtest: print """\ ****************************************** \tTests of splint and spalde ******************************************""" test2() test2(per=1) test2(ia=0.2*pi,ib=pi) test2(ia=0.2*pi,ib=pi,N=50) if 3 in runtest: print """\ ****************************************** \tTests of sproot ******************************************""" test3(a=0,b=15) print "Note that if k is not 3, some roots are missed or incorrect" if 4 in runtest: print """\ ****************************************** \tTests of splprep, splrep, and splev ******************************************""" test4() test4(N=50) if 5 in runtest: print """\ ****************************************** \tTests of bisplrep, bisplev ******************************************""" test5()