fixes issue #9 - histogram of equal values returns Infinity

Explicitly set bin size to 1 for all arrays with the same value, regardless of
the size.  That deals with this case (and many other similar cases to it).

lib/histogram.rb

@@ -88,11 +88,15 @@ def median(sorted)
   #
   # middle is the median between the other three values
   #
+  # Note: always returns 1 if all values are the same.
+  #
   # inspired by {Richard Cotton's matlab
   # implementation}[http://www.mathworks.com/matlabcentral/fileexchange/21033-calculate-number-of-bins-for-histogram]
   # and the {histogram page on
   # wikipedia}[http://en.wikipedia.org/wiki/Histogram]
   def number_of_bins(methd=DEFAULT_BIN_METHOD, quartile_method=DEFAULT_QUARTILE_METHOD)
+    return 1 if self.to_a.uniq.size == 1
+
     if methd == :middle
       [:scott, :sturges, :fd].map {|v| number_of_bins(v) }.sort[1]
     else
@@ -171,6 +175,8 @@ def number_of_bins(methd=DEFAULT_BIN_METHOD, quartile_method=DEFAULT_QUARTILE_ME
   #   (so, values lower than first bin are not included, but all values
   #   higher, than last bin are included.  Current implementation of custom
   #   bins is slow.
+  # * If the number of bins must be determined and all values are the same,
+  #   will use 1 bin.
   # * if other_sets are supplied, the same bins will be used for all the sets.
   #   It is useful if you just want a certain number of bins and for the sets
   #   to share the exact same bins. In this case returns [bins, freqs(caller),

lib/histogram/version.rb

@@ -1,3 +1,3 @@
 module Histogram
-  VERSION = "0.2.3.0"
+  VERSION = "0.2.4.0"
 end

spec/histogram_spec.rb

@@ -110,6 +110,12 @@ def round(n=nil)
     bins, freq = obj8.histogram
   end
 
+  it 'uses 1 bin if all values are the same' do
+    bins, freq = obj6.histogram(:sturges)
+    bins.to_a.should == [0]
+    freq.to_a.should == [5]
+  end
+
 end
 
 describe Histogram do