score:0

If you are looking for a way to show a tooltip for a specific element by clicking on a button you may take a look to github or SO

I changed a bit the code I found there just to let you show a tooltip on button click.

I added a property to your options in Chartjs:

showMyTooltips: '',

This must contain the index of the tooltip to be shown. This value is used inside the registered plugin like in the example code whose links are reported in this answer.

Here is the snippet:

Chart.pluginService.register({
    beforeRender: function (chart) {
        if (!!chart.config.options.showMyTooltips && chart.config.options.showMyTooltips.trim().length != 0) {
            chart.pluginTooltips = [];
            chart.config.options.showMyTooltips.trim().split(',').forEach(function (ele, idx) {
                var sector = chart.getDatasetMeta(0).data[ele];
                chart.pluginTooltips.push(new Chart.Tooltip({
                    _chart: chart.chart,
                    _chartInstance: chart,
                    _data: chart.data,
                    _options: chart.options.tooltips,
                    _active: [sector]
                }, chart));
            });
        }
    },
    afterDraw: function (chart, easing) {
        if (chart.config.options.showMyTooltips) {
            // we don't want the permanent tooltips to animate, so don't do anything till the animation runs atleast once
            if (!chart.allTooltipsOnce) {
                if (easing !== 1)
                    return;
                chart.allTooltipsOnce = true;
            }
            Chart.helpers.each(chart.pluginTooltips, function (tooltip) {
                tooltip.initialize();
                tooltip.update();
                // we don't actually need this since we are not animating tooltips
                tooltip.pivot();
                tooltip.transition(easing).draw();
            });
        }
    }
});

var ctx = document.getElementById('ctx').getContext('2d');
var ocacolor = '#EE8B54',
        ocbcolor = '#C2B49B',
        ocbacolor = '#AECF86',
        ocgcolor = '#E97676',
        ocpcolor = '#088DA5';
var backgroundcolor = [ocacolor, ocbcolor, ocbacolor, ocgcolor, ocpcolor]

data = {
    datasets: [{
        data: [5, 2, 3, 9, 2],
        backgroundColor: backgroundcolor
    }],
    labels: [
        'OCA',
        'OCB',
        'OCBA',
        'OCG',
        'OCP'
    ]
};
//CREATING CHART
var myDoughnutChart = new Chart(ctx, {
    type: 'doughnut',
    data: data,
    options: {
        legend: {
            display: false
        },
        showMyTooltips: '',
        onClick: function (evt, dataset) {
            //I GET THE LABEL TEXT OF THE CLICKED ITEM
            console.log(dataset[0]._model.label);
        }
    }
});

$(":radio").on('change', function (e) {
    myDoughnutChart.options.showMyTooltips = myDoughnutChart.data.labels.indexOf(this.id).toString();
    myDoughnutChart.update(true);
})
.graph{
    height: 500px;
    width: 500px;
    text-align: center;
}
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css">
<script src="https://code.jquery.com/jquery-3.3.1.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.3/umd/popper.min.js"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/js/bootstrap.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.7.2/Chart.min.js"></script>


<div class="graph">
    <canvas id="ctx"></canvas>
    <div class="btn-group btn-group-toggle" data-toggle="buttons">
        <label class="btn btn-secondary">
            <input type="radio" name="options" id="OCA" autocomplete="off"> Test OCA
        </label>
        <label class="btn btn-secondary">
            <input type="radio" name="options" id="OCB" autocomplete="off"> Test OCB
        </label>
        <label class="btn btn-secondary">
            <input type="radio" name="options" id="OCBA" autocomplete="off"> Test OCBA
        </label>
        <label class="btn btn-secondary">
            <input type="radio" name="options" id="OCG" autocomplete="off"> Test OCG
        </label>
        <label class="btn btn-secondary">
            <input type="radio" name="options" id="OCP" autocomplete="off"> Test OCP
        </label>
    </div>
</div>


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