Question

Another task for underscore.js – I need to do ‘calibrate’ the data, for displaying it in the chart.

Given: available space: 160 and data: data: [10, 50, 80, 90] I want to get calibratedData: [0, 80, 140, 160].

here’s the algorithm:

1. get the peaks for the data, Min=10 , Max = 90.
2. get the difference between Min and Max, 80.
3. get the Unit space available to 1 unit of change as 160 / 80 = 2
4. calibrate each item in data, using the ratio from the previous step as:
   d[i] = (d[i]-Min) * Unit, which gives [0, 80, 140, 160].

Wonder if I can accomplish the task using ‘linq’able syntax of underscore.js.

Answer 1

I don’t understand why people downvoted your question, but it was fun to find the answer. Here it is:

function calibrate( data, availableSpace ) {
    var min = _.min(data);
    var max = _.max(data);
    var range = max - min;
    var spacePerUnit = availableSpace / range;
    return _.map( data, function (value) {
        return ( value - min ) * spacePerUnit;
    });
}

alert( calibrate( [10, 50, 80, 90], 160 ) );

You can try it in this JSFiddle.

The key is to use the map() function in Underscore with this function:

function (value) {
  return ( value - min ) * spacePerUnit;
}

This function has access to the min, max and spacePerUnit values in the parent function which makes it very efficient (because it doesn’t do the calculations in every iteration).