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module Rubyvis
# Represents an ordinal scale. <style
# type="text/css">sub{line-height:0}</style> An ordinal scale represents a
# pairwise mapping from <i>n</i> discrete values in the input domain to
# <i>n</i> discrete values in the output range. For example, an ordinal scale
# might map a domain of species ["setosa", "versicolor", "virginica"] to colors
# ["red", "green", "blue"]. Thus, saying
#
# .fill_style(lambda {|d|
# case (d.species)
# when "setosa"
# "red"
# when "versicolor"
# "green"
# when "virginica"
# "blue"
# }
# )
#
# is equivalent to
#
# .fill_style(Rubyvis::Scale.ordinal("setosa", "versicolor", "virginica")
# .range("red", "green", "blue")
# .by(lambda {|d| d.species}))</pre>
#
# If the mapping from species to color does not need to be specified
# explicitly, the domain can be omitted. In this case it will be inferred
# lazily from the data:
#
# .fill_style(Rubyvis.colors("red", "green", "blue")
# .by(lambda {|d| d.species}))</pre>
#
# When the domain is inferred, the first time the scale is invoked, the first
# element from the range will be returned. Subsequent calls with unique values
# will return subsequent elements from the range. If the inferred domain grows
# larger than the range, range values will be reused. However, it is strongly
# recommended that the domain and the range contain the same number of
# elements.
#
# A range can be discretized from a continuous interval (e.g., for pixel
# positioning) by using split, split_flush or
# split_banded after the domain has been set. For example, if
# <tt>states</tt> is an array of the fifty U.S. state names, the state name can
# be encoded in the left position:
#
# .left(Rubyvis::Scale.ordinal(states)
# .split(0, 640)
# .by(lambda {|d| d.state}))
#
# N.B.: ordinal scales are not invertible (at least not yet), since the
# domain and range and discontinuous. A workaround is to use a linear scale.
class Scale::Ordinal
# range band, after use split_banded
# equivalen to protovis scale.range().band
attr_reader :range_band
# Returns an ordinal scale for the specified domain. The arguments to this
# constructor are optional, and equivalent to calling domain
def initialize(*args)
@d=[] # domain
@i={}
@r=[]
@range_band=nil
@band=0
domain(*args)
end
# Return
# lambda {|d| scale_object.scale(d)}
# Useful as value on dynamic properties
# scale=Rubyvis.ordinal("red","blue","green")
# bar.fill_style(scale)
# is the same as
# bar.fill_style(lambda {|x| scale.scale(x)})
def to_proc
that=self
lambda {|*args| args[0] ? that.scale(args[0]) : nil }
end
def scale(x)
if @i[x].nil?
@d.push(x)
@i[x]=@d.size-1
end
@r[@i[x] % @r.size]
end
alias :[] :scale
# Sets or gets the input domain. This method can be invoked several ways:
#
# <p>1. <tt>domain(values...)</tt>
#
# <p>Specifying the domain as a series of values is the most explicit and
# recommended approach. However, if the domain values are derived from data,
# you may find the second method more appropriate.
#
# <p>2. <tt>domain(array, f)</tt>
#
# <p>Rather than enumerating the domain values as explicit arguments to this
# method, you can specify a single argument of an array. In addition, you can
# specify an optional accessor function to extract the domain values from the
# array.
#
# <p>3. <tt>domain()</tt>
#
# <p>Invoking the <tt>domain</tt> method with no arguments returns the
# current domain as an array.
def domain(*arguments)
array, f=arguments[0],arguments[1]
if(arguments.size>0)
array= (array.is_a? Array) ? ((arguments.size>1) ? Rubyvis.map(array,f) : array) : arguments.dup
@d=array.uniq
@i=Rubyvis.numerate(@d)
return self
end
@d
end
# Sets the range from the given continuous interval. The interval [<i>
# min</i>, <i>max</i>] is subdivided into <i>n</i> equispaced bands,
# where <i>n</i> is the number of (unique) values in the domain. The first
# and last band are offset from the edge of the range by the distance between bands.
#
# <p>The band width argument, <tt>band</tt>, is typically in the range [0, 1]
# and defaults to 1. This fraction corresponds to the amount of space in the
# range to allocate to the bands, as opposed to padding. A value of 0.5
# means that the band width will be equal to the padding width.
# The computed absolute band width can be retrieved from the range as
# <tt>scale.range_band</tt>.
#
# <p>If the band width argument is negative, this method will allocate bands
# of a <i>fixed</i> width <tt>-band</tt>, rather than a relative fraction of
# the available space.
#
# <p>Tip: to inset the bands by a fixed amount <tt>p</tt>, specify a minimum
# value of <tt>min + p</tt> (or simply <tt>p</tt>, if <tt>min</tt> is
# 0). Then set the mark width to <tt>scale.range_band - p</tt>.
#
# <p>This method must be called <i>after</i> the domain is set.
def split_banded(*arguments) # :args: (min,max,band=1)
min,max,band=arguments
band=1 if (arguments.size < 3)
if (band < 0)
n = self.domain().size
total = -band * n
remaining = max - min - total
padding = remaining / (n + 1).to_f
@r = Rubyvis.range(min + padding, max, padding - band);
@range_band = -band;
else
step = (max - min) / (self.domain().size + (1 - band))
@r = Rubyvis.range(min + step * (1 - band), max, step);
@range_band = step * band;
end
return self
end
def range(*arguments)
array, f = arguments[0],arguments[1]
if(arguments.size>0)
@r=(array.is_a? Array) ? ((arguments.size>1) ? array.map(&f) : array) : arguments.dup
if @r[0].is_a? String
@r=@r.map {|i| Rubyvis.color(i)}
end
return self
end
@r
end
# Sets the range from the given continuous interval. The interval [<i>
# min</i>, <i>max</i>] is subdivided into <i>n</i> equispaced points,
# where <i>n</i> is the number of (unique) values in the domain. The first
# and last point are offset from the edge of the range by half the distance
# between points.
#
# <p>This method must be called <i>after</i> the domain is set.
def split(min,max)
step=(max-min).quo(domain().size)
@r=Rubyvis.range(min+step.quo(2),max,step)
self
end
# Sets the range from the given continuous interval. The interval
# [<i>min</i>, <i>max</i>] is subdivided into <i>n</i> equispaced points,
# where <i>n</i> is the number of (unique) values in the domain. The first
# and last point are exactly on the edge of the range.
#
# <p>This method must be called <i>after</i> the domain is set.
#
# * @param {number} min minimum value of the output range.
# * @param {number} max maximum value of the output range.
# * @returns {pv.Scale.ordinal} <tt>this</tt>.
# * @see Ordinal.split
def split_flush(min,max)
n = self.domain().size
step = (max - min) / (n - 1).to_f
@r = (n == 1) ? [(min + max) / 2.0] : Rubyvis.range(min, max + step/2.0, step)
self
end
def by(f)
that=self
lambda {|*args|
that.scale(f.js_apply(self,args))
}
end
end
end
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