 
 ColorMapper = require "./color_mapper"
 
+# Math.log1p() is not supported by any version of IE, so let's use a polyfill based on
+# https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/log1p.
+log1p = Math.log1p ? (x) -> Math.log(1 + x)
 
 class LogColorMapper extends ColorMapper.Model
   type: "LogColorMapper"

    n = palette.length
    low = @low ? _.min(data)
    high = @high ? _.max(data)
    scale = n / (Math.log1p(high) - Math.log1p(low))  # subtract the low offset
    max_key = palette.length - 1
    values = []


        continue

      # Get the key
      log = log1p(d) - log1p(low)  # subtract the low offset
      key = Math.floor(log * scale)

      # Deal with upper bound
