[Feature Request] Retrieve data from chart

[BambOoxX]

It seems that this great package has no interface to retrieve data from a chart contained in an Excel file. This would be a great addition I believe, especially since the package already explores the file tree of XLSX files that includes the XML files associated with the charts.

[TimG1964]

Could you clarify what you are hoping for here? An Excel chart displays data that are held in regular worksheet cells (doesn't it?) and XLSX.jl can read data in regular cells. So it can access the same data as the chart is displaying.

Is there some other type of chart data that you have in mind?

[BambOoxX]

I think (I have to remember) it was because the original data from these charts were from an external file that was not available anymore (like on a distant folder).
This resulted in having the data in the charts, but not available explicitly in the sheets.

[TimG1964]

Were these charts simple images or actually native charts? If the latter, the data must have been (?) in a linked data source. Would be useful to have an actual example.

[BambOoxX]

These were native charts. I could reproduce this with a simple example file attached.

TestFile.xlsx

[TimG1964]

Thank you for the example. I can see that the chart is based on data referenced in a separate data source (separate spreadsheet). It is cached inside the chart's xml file, too, and it would be possible, in principle, to read this cached data.

This seems to me to be something that is not frequently required. I'll mark it as an enhancement but I don't think it will be high on my priority list. I'd welcome a PR to do this if anyone is keen to make one.

[BambOoxX]

This seems to me to be something that is not frequently required. I'll mark it as an enhancement but I don't think it will be high on my priority list. I'd welcome a PR to do this if anyone is keen to make one.

Totally agreed ^^. If you have some pointers, to check where this data can be located, I could try to propose a PR.

[TimG1964]

This is not something I've investigated but expect lots of complexity if you want to deal with all options. Any PR should aim for as much generality as possible (eg all plot types, not just line charts).

In your example, and inside the zip archive that is the XLSX file, you will find xl\charts\chart1.xml which describes this chart and the data are cached in there.

I don't know if the same xml structure is used if the chart is within an existing sheet rather than being a sheet in its own right.