since095 since095 - 1 year ago 73
Javascript Question

Update position/transition from last value (guage chart / d3.js)

I'm trying to repurpose a guage chart I found here. Currently I have the needle moving on submit, however it resets to 0 before updating to the new position, I'd rather it just adjust the position directly.

When trying to think of a way to do it, I figured that I would need to modifiy this snippet of code which handles the reset;

Needle.prototype.moveTo = function(perc) {
var self,
oldValue = this.perc || 0;

this.perc = perc;
self = this;

// Reset pointer position
this.el.transition().delay(100).ease('quad').duration(200).select('.needle').tween('reset-progress', function() {
return function(percentOfPercent) {
var progress = (1 - percentOfPercent) * oldValue;

return'd',, progress));

this.el.transition().delay(300).ease('bounce').duration(1500).select('.needle').tween('progress', function() {
return function(percentOfPercent) {
var progress = percentOfPercent * perc;

return'd',, progress));


return Needle;



So I think, I am going to have to find a way of remember the old value before updating instead of resetting to 0, or just try remove the reset function completely?

But I'm not really sure how I can achieve that.

Here is the update function;

function updateNeedle() {
var value = 90;
var percentValue = value / gaugeMaxValue;
percent = percentValue;

I have made a plnk, and tried to strip out everything not relevant to the question to reduce the code, just click the submit to update the position and hopefully the question will make sense.

I think this all might be a bit hacky, but i'm hoping someone can help anyway!


Answer Source

I changed your moveTo function. It was using progress starting from 0. So, I change to this:

var progress = oldValue + (percentOfPercent * (perc - oldValue));

Here is the plunker:

I made this other plunker setting the value to a random number when the user clicks "submit", using var value = Math.random()*100. I believe it's working the way you want, check it:

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