Document method of truncating decimals

Expected Behavior

An option to truncate decimals.

Current Behavior

Currently many decimals are being displayed when hovering over a datapoint. I have no problem of them being used in calculating positions but for display purposes it would be nice to be able to truncate some decimals.
chart_js_significant_digits

Possible Solution

Implement an option to allow truncation of decimals.

Context

Many decimals are not always useful when showing a graph to another person.

Environment

  • Chart.js version: 2.7.1
  • Browser name and version: Firefox 52.4.0 ESR

Author: Fantashit

1 thought on “Document method of truncating decimals

  1. You could add a personalized callback to the tooltip labels, where you round the values
    e.g.

    1. tooltipItem.yLabel.toFixed(2) would return a value with 2 decimal places.
    2.123.toFixed(2)
    >> "2.12"
    2.0001.toFixed(2)
    >> "2.00"
    
    1. Math.round(tooltipItem.yLabel * 100) / 100 would return a value rounded to the nearest 2nd decimal place.
    Math.round(2.123 * 100) / 100
    >> 2.12
    Math.round(2.00001 * 100) / 100
    >> 2
    
    tooltips: {
        callbacks: {
            label: function(tooltipItem, data) {
                var label = data.datasets[tooltipItem.datasetIndex].label || '';
    
                if (label) {
                    label += ': ';
                }
                label += tooltipItem.yLabel.toFixed(2);
                return label;
            }
        }
    }

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