Flot: How do I grab the nearest plotted point to where the cursor is?

flot, javascript

Solution

What's your use case for this? If you increase the `mouseActiveRadius` option to something large flot will find the closest point to the cursor for you.

var options = {
    grid: { 
        hoverable: true, 
        mouseActiveRadius: 1000
    }
}

Example here.

EDIT

Yes, you can use the `plothover` event to retrieve the highlighted point.

$("#placeholder").bind("plothover", function (event, pos, item) {
    if (item){
        var x = item.datapoint[0].toFixed(2),
            y = item.datapoint[1].toFixed(2);
        console.log("x:" + x + ", " + "y:" + y);
    }
});

Updated Fiddle here.

Problem

I am trying to grab the nearest plotted point that the cursor is to. I I found the `findNearbyItem` function in the `jquery.flot.js` source that seems to be able to do this, but when I trie calling it manually, I received the `ReferenceError: findNearbyItem is not defined` error. This is the function I am referring to: ``` function findNearbyItem(mouseX, mouseY, seriesFilter) { var maxDistance = options.grid.mouseActiveRadius, smallestDistance = maxDistance * maxDistance + 1, item = null, foundPoint = false, i, j, ps; for (i = series.length - 1; i >= 0; --i) { if (!seriesFilter(series[i])) continue; var s = series[i], axisx = s.xaxis, axisy = s.yaxis, points = s.datapoints.points, mx = axisx.c2p(mouseX), // precompute some stuff to make the loop faster my = axisy.c2p(mouseY), maxx = maxDistance / axisx.scale, maxy = maxDistance / axisy.scale; ps = s.datapoints.pointsize; // with inverse transforms, we can't use the maxx/maxy // optimization, sadly if (axisx.options.inverseTransform) maxx = Number.MAX_VALUE; if (axisy.options.inverseTransform) maxy = Number.MAX_VALUE; if (s.lines.show || s.points.show) { for (j = 0; j < points.length; j += ps) { var x = points[j], y = points[j + 1]; if (x == null) continue; // For points and lines, the cursor must be within a // certain distance to the data point if (x - mx > maxx || x - mx < -maxx || y - my > maxy || y - my < -maxy) continue; // We have to calculate distances in pixels, not in // data units, because the scales of the axes may be different var dx = Math.abs(axisx.p2c(x) - mouseX), dy = Math.abs(axisy.p2c(y) - mouseY), dist = dx * dx + dy * dy; // we save the sqrt // use <= to ensure last point takes precedence // (last generally means on top of) if (dist < smallestDistance) { smallestDistance = dist; item = [i, j / ps]; } } } if (s.bars.show && !item) { // no other point can be nearby var barLeft = s.bars.align == "left" ? 0 : -s.bars.barWidth/2, barRight = barLeft + s.bars.barWidth; for (j = 0; j < points.length; j += ps) { var x = points[j], y = points[j + 1], b = points[j + 2]; if (x == null) continue; // for a bar graph, the cursor must be inside the bar if (series[i].bars.horizontal ? (mx <= Math.max(b, x) && mx >= Math.min(b, x) && my >= y + barLeft && my <= y + barRight) : (mx >= x + barLeft && mx <= x + barRight && my >= Math.min(b, y) && my <= Math.max(b, y))) item = [i, j / ps]; } } } if (item) { i = item[0]; j = item[1]; ps = series[i].datapoints.pointsize; return { datapoint: series[i].datapoints.points.slice(j * ps, (j + 1) * ps), dataIndex: j, series: series[i], seriesIndex: i }; } return null; } ``` If there are alternate ways of solving this problem, please let me know.

Original source