Highstock cumulative line series y axis labels are wrong

[mirkori]

Expected behaviour

If i have lots of line data (1000+ data points) and want to view the cumulative line plot, the y axis labels should be correct independent of the chart width.

Actual behaviour

The y axis value is displayed incorrectly if the chart is not wide enough.

Live demo with steps to reproduce

This example demonstrates the y axis labels incorrectly displayed for cumulative line data with values 1 to 1000.

It shows three charts rendering the same data but with different widths.
The top y axis labels should all be about 500k (sum of 1 to 1000) but only the first chart (2000px wide) actually displays the correct label.
The second and third chart (1000px and 200px wide) display incorrect y axis labels.

https://jsfiddle.net/tgaepxqy/1/

Product version

Highstock JS v11.0.1 (2023-05-08)

Affected browser(s)

Chrome (112.0.5615.137), Firefox (112.0.2), Safari (16.4)

[faebuk]

I think the problem is with data grouping of Highcharts.

You can fix the issue using the following configuration.

dataGrouping: {
    enabled: false
}

[karolkolodziej]

Hi @mirkori, @faebuk is right this behaves differently because of the dataGrouping -demo.

Internal note:
IMO the cumulative API documentation and Cumulative docs need improvement- It should inform how this behaves when the dataGrouping enabled.

[pawelfus]

sum approximation should be the default one for cumulativeSum series - we need to change it in the core

Demo: https://jsfiddle.net/BlackLabel/Lwrxagfe/