How can I scale my dataset values as a percentage of the index in chart.js? - chart.js

Question

Sorry if the question is poorly worded.Here is my chart
I am looking into scaling the chart's display of dataset(s) values as a percentage such as:
//input
data:{
datasets[{
label: 'data1',
data: [15, 22, 18, 35, 16, 29, 40]
},
{
label: 'data2',
data: [20, 21, 20, 19, 21, 22, 35]
}]
data1's points on the chart would be displayed as [42.9, 51.2, 47.4, 64.8, 43.2, 56.9, 57.1]
data2's points on the chart would be displayed as [57.1, 48.8, 52.6, 35.2, 56.8, 43.1, 42.9]
It should look like this. All visible lines should stack up to 100%. If a dataset is hidden, how can I recalculate the percentage and update the chart so that everything stays stacked up to 100%?
I thought about doing a plugin where I do the calculation using myLine.data.datasets but then I don't know how to remove a hidden dataset's values from the calculation and I'm not sure how to display it unless I overwrite the original datasets. I'm pretty sure this is the wrong approach.
Any help would be greatly appreciated.

Answer 1

So, I figured it out. I needed to write a function to calculate the percentage area of the points in the index and then update the datasets with the calculated percentage values.
/*+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
*
* DS_update calculates the percentage area of the input datasets
*
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++*/
function DS_update(dataset_in, ds_vis){
// make a deep copy (no references to the source)
var temp = jQuery.extend(true, [], dataset_in);
// gets the sum of all datasets at a given index
function getTotal(index){
total = 0;
// step through the datasets
dataset_in.forEach(function(e, i){
// inc total if the dataset is visible
if(ds_vis[i]){
total += e[index];
}
// do nothing if the dataset is hidden
});
return total;
}
// update temp array with calculated percentage values
temp.forEach(function(el, ind){
var j = ind;
el.forEach(function(e, i){
// calculate percentage to the hundredths place
temp[j][i] = Math.round((e / getTotal(i))*10000)/100;
});
});
return temp;
}
Once I tested the functions I had to run them before initial load of the chart or else the user would see the datasets as non area-percent (raw data). which looks something like this:
// Keep source array to use in the tool tips
var Src_ary = Input_data; // multidimensional array of input data
// holds the percent-area calculations as datapoints
var Prod_ary = DS_update(Src_ary, Init_visible(Src_ary));
Next up was updating the onClick for the legend. I need this to update the calculations every time an item's visibility is toggled:
legend: {
position: 'bottom',
usePointStyle: true,
onClick:
function(e, legendItem){
var index = legendItem.datasetIndex;
var ci = this.chart;
var meta = ci.getDatasetMeta(index);
var vis_ary = [];
var updatedSet = [];
// See controller.isDatasetVisible comment
meta.hidden = meta.hidden === null? !ci.data.datasets[index].hidden : null;
// load the visible array
for(var i = 0; i < (ci.data.datasets || []).length; i++){
switch (ci.getDatasetMeta(i).hidden){
case null:
vis_ary.push(true);
break;
default:
vis_ary.push(false);
break;
}
}
// update datasets using vis_ary to tell us which sets are visible
updatedSet = DS_update(Prod_ary, vis_ary);
myLine.data.datasets.forEach(function (e,i){
e.data = updatedSet[i];
});
// We did stuff ... rerender the chart
ci.update();
}
}
END RESULT
This is what I was trying to do: highchart fiddle
This is what I ended up with:fiddle
It took a few days and a lot of reading through chartjs.org's documentation to put this together. In the end I think it came out pretty good considering I am new to chart.js and borderline illiterate with javascript.