Question

I have custom control – chart with size, for example, 300×300 pixels and more than one million points (maybe less) in it. And its clear that now he works very slowly. I am searching for algoritm which will show only few points with minimal visual difference.

I have a link to the component which have functionallity exactly what i need
(2 million points demo):

I will be grateful for any matherials, links or thoughts how to realize such functionallity.

Answer 1

If I understand your question correctly, then you are looking to plot a graph of a dataset where you have ~1M points, but the chart’s horizontal resolution is much smaller? If so, you can down-sample your dataset to get about the number of available x values. If your data is sorted in equal intervals, you can extract every N’th point and plot it. Choose N such that the number of points is, say, double the resolution (in this case, N=2000 will give you 500 points to display).

If the intervals are very different from eachother (not regularly spaced), you can approximate your graph with a polynomial, or spline or any other method that fits, and then interpolate 300-600 points from that approximation.

EDIT:

Depending on the nature of the data, you may end up with aliasing artifacts when you simply sample every N’t point. There are probably better methods for coping with this problem, but again – it depends on what exactly you want to plot.