[feature request] render xAxis like yAxis style Namely from discrete way to continuous way

[liuxuan30]

Is it possible that scatter chart view or all charts render the xAxis and the data in a 'continuous' way rather than 'discrete' way?

For example, if the xValues is [31.2,67.8,75.3,80.9,120] and the yValues is [12,16,30,80,200]

if we draw this chart, the horizontal space will be equal to each data point; but it does not reflect the true distance for the xValues.

what I want the xAxis rendering is using the same concept for yAxis, using ratio ( dataValue / (yAxis.maxValue - yAxis.minValue) * factor), so it reflect the correct position.

@danielgindi I am not sure if you had heard such requirements; but if I do need to do this by myself, is there any documentation of how the yAxis render works, like the zooming/scrolling feature? The original android wiki is not in detail.

By the way, I was curious, how you draw the sin function line chart on the home page? It looks quite smooth, with such a smooth curve, do you really generate thouds of xValues?

[danielgindi]

Well I don't know about the axis - I think @PhilJay could help you here more than I could...
But about the sine function - it's pretty simple: You could play with cubic lines... or add lot's of point :-)

[liuxuan30]

I have figure it out! I make use of the horizontal bar chart right Axis and changed the transformer setup. It works like a charm. The key point is render it like the y axis style, not by isolated index style.

[liuxuan30]

@danielgindi and @PhilJay I do recommend you consider this, as there is actual needs for rendering xAxis like yAxis. Current xAxis limitation is it is using index to draw.

For example, when the xAxis represents date & time, I have data '10.0' at 07:05am, and have '20.0' at 07:05pm. If we use index technique, to reflect the xAxis span from 00:00 to 23:59, I have to insert many null point on each minute point, to reflect the correct ratio on x axis. Finally the for loop will be the bottleneck when drawing, if the date range is a big number

However, If we just calculate the time range, and we can calculate the ratio on x axis, we can simply only render two data, don't have to insert many null values to have the same result.

[liuxuan30]

I tried to do it on my side, just take the ChartYAxisRendererHorizontalBarChart as xAxis, change the transformer CTM, and disable xAxis. However, this can lead to some conflicts such as enabling autoScaleMinMax will result in an empty chart. I am not as familiar as you genius with the transformer (CTM) stuff and some features, so it's better that you guys can do it. No offence, but I will definitely donate what I can afford to support developing this feature. How do you think?

[danielgindi]

This is a duplicate of #194 actually...
As long as those issues are open it means we do want to do them. It's just complicated :-)

[danielgindi]

Btw @liuxuan30 the transformation matrices are simple math; Implementing this feature requires something more algorithmic than just simple math. Not something complex mathmatically - just different, which means changing the transformer code to not use those matrices, and lots and lots of testing.

@PhilJay any news on your side?

[liuxuan30]

@danielgindi Acutally I am the first one to ask this, so #194 is duplicated :-)

I just make use of the horizontal bar yAxis to do it right now.

Yes, I think it's more than transformer math while I am trying. the zooming and scrolling is killing me. I cannot find a way to correctly render the xAxis labels in the right position.