Class: Rubyvis::Scale::Log

Inherits:
Quantitative show all
Defined in:
lib/rubyvis/scale/log.rb

Instance Attribute Summary

Attributes inherited from Quantitative

#l

Instance Method Summary collapse

Methods inherited from Quantitative

#by, #domain, #invert, #new_date, #range, #scale, #tick_format, #to_date, #to_proc, #type

Methods included from Rubyvis::Scale

interpolator, linear, log, ordinal, quantitative

Constructor Details

#initialize(*args) ⇒ Log

Returns a new instance of Log.

Raises:

  • (ArgumentError) 


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# File 'lib/rubyvis/scale/log.rb', line 4

def initialize(*args)
  super(*args)
  raise(ArgumentError,"left side of domain should be >0") if(@d.first<=0)
  @b=nil
  @_p=nil
  base(10)
end

Instance Method Details

#base(v = nil) ⇒ Object 



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# File 'lib/rubyvis/scale/log.rb', line 17

def base(v=nil)
  if v
    @b=v
    @_p=Math.log(@b)
    transform(lambda {|x| log(x)}, lambda {|x| pow(x)})
    return self
  end
  return @b
end

#log(x) ⇒ Object 



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# File 'lib/rubyvis/scale/log.rb', line 11

def log(x)
  Math.log(x) / @_p.to_f
end

#nice ⇒ Object 



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# File 'lib/rubyvis/scale/log.rb', line 26

def nice
  d=domain
  domain(Rubyvis.log_floor(d[0],@b), Rubyvis.log_ceil(d[1],@b))
end

#pow(y) ⇒ Object 



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# File 'lib/rubyvis/scale/log.rb', line 14

def pow(y)
  @b**y
end

#ticks(subdivisions = nil) ⇒ Object

Returns an array of evenly-spaced, suitably-rounded values in the input domain. These values are frequently used in conjunction with Rule to display tick marks or grid lines.

Subdivisions set the number of division inside each base^x By default, is set to base



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# File 'lib/rubyvis/scale/log.rb', line 36

def ticks(subdivisions=nil)
  d = domain
  n = d[0] < 0
  subdivisions||=@b
  span=@b.to_f / subdivisions
 # puts "dom: #{d[0]} -> #{n}"
  
  i = (n ? -log(-d[0]) : log(d[0])).floor
  j = (n ? -log(-d[1]) : log(d[1])).ceil
  ticks = [];
  if n
    ticks.push(-pow(-i))
    (i..j).each {|ii|
      ((@b-1)...0).each {|k|
        ticks.push(-pow(-ii) * k)
      }
    }
  else
    (i...j).each {|ii|
      (1..subdivisions).each {|k|
        if k==1
          ticks.push(pow(ii))
        else
          next if subdivisions==@b and k==2
          ticks.push(pow(ii)*span*(k-1))
        end
      }
    }
    ticks.push(pow(j));
  end
  
  # for (i = 0; ticks[i] < d[0]; i++); // strip small values
  # for (j = ticks.length; ticks[j - 1] > d[1]; j--); // strip big values
  # return ticks.slice(i, j);
  ticks.find_all {|v| v>=d[0] and v<=d[1]}
end