function getIsInContinuousRange(dataExtent, range) {
	        var dataSpan = dataExtent[1] - dataExtent[0];
	        range = [
	            (range[0] - dataExtent[0]) / dataSpan,
	            (range[1] - dataExtent[0]) / dataSpan
	        ];
	        return function (val) {
	            return val >= range[0] && val <= range[1];
	        };
	    }
@file defines echarts Heatmap Chart
@author Ovilia (me@zhangwenli.com)
Inspired by https://github.com/mourner/simpleheat

@module