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## Copyright (C) 1996 John W. Eaton
##
## This file is part of Octave.
##
## Octave is free software; you can redistribute it and/or modify it
## under the terms of the GNU General Public License as published by
## the Free Software Foundation; either version 2, or (at your option)
## any later version.
##
## Octave is distributed in the hope that it will be useful, but
## WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
## General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with Octave; see the file COPYING. If not, write to the Free
## Software Foundation, 59 Temple Place - Suite 330, Boston, MA
## 02111-1307, USA.
## usage: [xs, ys] = stairs (x, y)
##
## Given two vectors of x-y data, stairs produces a `stairstep' plot.
##
## If only one argument is given, it is taken as a vector of y-values
## and the x coordiates are taken to be the indices of the elements.
##
## If two output arguments are specified, the data are generated but
## not plotted. For example,
##
## stairs (x, y);
##
## and
##
## [xs, ys] = stairs (x, y);
## plot (xs, ys);
##
## are equivalent.
##
## See also: plot, semilogx, semilogy, loglog, polar, mesh, contour,
## bar, gplot, gsplot, replot, xlabel, ylabel, title
## Author: jwe
function [xs, ys] = stairs (x, y)
if (nargin == 1)
if (is_vector (x))
len = 2 * length (x);
tmp_xs = tmp_ys = zeros (len, 1);
k = 0;
for i = 1:2:len
tmp_xs(i) = k++;
tmp_ys(i) = x(k);
tmp_ys(i+1) = x(k);
tmp_xs(i+1) = k;
endfor
else
error ("stairs: argument must be a vector");
endif
elseif (nargin == 2)
if (is_vector (x) && is_vector (y))
xlen = length (x);
ylen = length (y);
if (xlen == ylen)
len = 2 * xlen;
tmp_xs = tmp_ys = zeros (len, 1);
k = 1;
len_m2 = len - 2;
for i = 1:2:len_m2
tmp_xs(i) = x(k);
tmp_ys(i) = y(k);
tmp_ys(i+1) = y(k);
k++;
tmp_xs(i+1) = x(k);
if (x(k) < x(k-1))
error ("stairs: x vector values must be in ascending order");
endif
endfor
tmp_xs(len-1) = x(xlen);
delta = x(xlen) - x(xlen-1);
tmp_xs(len) = x(xlen) + delta;
tmp_ys(len-1) = y(ylen);
tmp_ys(len) = y(ylen);
else
error ("stairs: arguments must be the same length");
endif
else
error ("stairs: arguments must be vectors");
endif
else
usage ("[xs, ys] = stairs (x, y)");
endif
if (nargout == 0)
plot (tmp_xs, tmp_ys);
else
xs = tmp_xs;
ys = tmp_ys;
endif
endfunction
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