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Drawing the chart a second time doesn't clear the previous chart

Posted by Roberto at 12:20 on Thursday 22nd April 2021 [link]
I should draw the graph and based on the input data updating the graph with the new data, and this works but draw the new bars on top of the old ones without gradually removing the bars of the previous graph, without updating the graph. How can I solve?

Posted by Richard at 16:24 on Thursday 22nd April 2021 [link]
You can use the RGraph.clear() function to clear the canvas before drawing a second time. For example:

var canvas = myObject.canvas;


PS. If you want an animated change then the Bar chart supports this by supplying the new data to the grow() function. There's an example here:


The code of which is this:

bar = new RGraph.Bar({
data: [8,4,6,3,5,4,2],
options: {
     backgroundGridVlines: false,
     backgroundGridBorder: false,
     yaxisScaleMax: 20

setInterval(function ()
    // count,min,max[,decimals]
    newData = RGraph.arrayRandom(7,0,20);

    bar.grow({data: newData});
}, 2000);


Posted by Roberto at 17:19 on Thursday 22nd April 2021 [link]
I tried to write:

var canvas = document.getElementById ('cvs');
RGraph.clear (canvas);

before redrawing the graph the second time but I don't update the graph.

Posted by Richard at 17:28 on Thursday 22nd April 2021 [link]
You then need to redraw the chart with either an animation function or the draw function like this:

var canvas = document.getElementById ('cvs'); // Or myObject.canvas works too

RGraph.clear (canvas); // Clear the canvas
myObject.draw();     // Redraw the chart

Posted by Roberto at 19:13 on Thursday 22nd April 2021 [link]
I tried but don't work.
I share the whole function so that you can check where the error is:

function mostraNascondiGrafico(arrayValGraficoAsseX, arrayDateLabelAsseX, arrayLimiti) {

    if ($('#divGraph').is(':visible')) {
     $("#buttMostrNascGrafico").text("MOSTRA GRAFICO");
     else {

     $("#buttMostrNascGrafico").text("NASCONDI GRAFICO");

//I entered the suggested lines here, is that correct?
    var canvas =document.getElementById('cvs');

    bar = new RGraph.Bar({
        id: 'cvs',
        data: arrayValGraficoAsseX,

        options: {

            yaxisScaleMax: 80,
            backgroundGridVlines: false,
            backgroundGridBorder: false,
            backgroundGridColor: '#999',
            xaxisLabels: arrayDateLabelAsseX,

            marginLeft: 55,
            marginRight: 55,
            marginBottom: 75,

            colors: ['Gradient(#A18AC5:#D1AAF5)'],
            textColor: '#ccc',
            xaxisTickmarksCount: 0,
            xaxis: false,
            yaxis: false,
            shadowColor: 'black',
            shadowOffsetx: 0,
            shadowOffsety: 0,
            shadowBlur: 15,
            colorsStroke: 'rgba(0,0,0,0)',
            combinedEffect: 'wave',
            combinedEffectOptions: '{frames: 30}'


    line = new RGraph.Line({
        id: 'cvs',
        data: arrayLimiti,
        options: {
            yaxisScaleMax: 80,
            xaxis: false,
            yaxis: false,
            backgroundGrid: false,
            colors: ['#d00'],
            yaxisPosition: 'right',
            textColor: '#ccc',
            marginLeft: 45,
            marginRight: 45,
            tickmarksStyle: null,
            spline: true,
            combinedEffect: 'trace',
            textSize: 18

    combo = new RGraph.CombinedChart([bar, line]).draw();

    // Poiche la classe combinata disattiva le etichette del grafico a linee,
    // le riattiva
        yaxisScale: true


    // Aggiunge alcune capacita di risposta al grafico a barre

         {maxWidth: null, width: 1400, height: 500, options: {textSize: 18, marginInner: 20}},
        {maxWidth: 1600, width: 1400, height: 500, options: {textSize: 12, marginInner: 7}}


        {maxWidth: null, width: 1400, height: 500, options: {textSize: 18, marginInner: 45, linewidth: 7}},
        {maxWidth: 1600, width: 1400, height: 500, options: {textSize: 12, marginInner: 20, linewidth: 5}}



Posted by Roberto at 20:32 on Thursday 22nd April 2021 [link]
solved, I used the reset () function instead of clear ()

[Replies are closed]