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Allow plotting on secondary y-axis #1272
Description
Using SQL page for my reporting on DuckDB
I would like to create compact graphs that show data series that have different scales of numbers on different axis.
What I would like is something like this on the data:
SELECT 'graph' as component, 'Small Number' AS ytitle, 'Large Numbers' AS ytitle2;
SELECT 'foo' AS series, 1 AS x, 10 as y, 1 as yaxis
UNION ALL
SELECT 'foo' AS series, 1 AS x, 20 as y, 1 as yaxis
UNION ALL
SELECT 'bar' AS series, 1 AS x, 100000 as y, 2 as yaxis
UNION ALL
SELECT 'bar' AS series, 1 AS x, 200000 as y, 2 as yaxis What I would now expect to happen is that the right side of the plot contains a secondary y-axis with 'Large Numbers' as the title and where the series 'bar' is plotted on that axis and series 'foo' is plotted on the first axis (titled: 'small number')
It can be an error to plot the same series on different y-axis - though that does not really have to be the case (the other choice is equally valid)
Activity
lovasoa commentedon Apr 8, 2026
Currently, sqlpage does not support secondary y axes, and I'm not sure it should. It tends to make unrelated or weakly related series look strongly correlated, and misrepresents series dynamics.
See for reference:
Depending on the use casen I'd recommend
thomaskejser commentedon Apr 8, 2026
That's a fair point (though IMHO highly subjective - Excel has been doing this for 50 years and nobody seems to mind).
If the alternative is to use two charts under each other, then one of these two features would be needed to that properly:
xmin/xmaxso i can make sure the graphs share the same width on the x axis and can be read and compared easilySharing of x-axis, but in two different plots on top of each other. For example, one could have this:
SELECT 'chart' AS component, 'first plot' AS ytitle, 'second plot' AS ytitle ; SELECT 'plot1' AS plot, 'foo' AS series, 1 AS x, 1000 AS y UNION ALL SELECT 'plot1' AS plot, 'foo' AS series, 1 AS x, 2000 AS y UNION ALL SELECT 'plot2' AS plot, 'foo' AS series, 1 AS x, 1 AS y UNION ALL SELECT 'plot12 AS plot, 'foo' AS series, 1 AS x, 2 AS yCards don't really solve this does it ?
lovasoa commentedon Apr 8, 2026
xmin and xmax should work already, but I see they are not documented ! I need to fix that
81reap commentedon Aug 13, 2026
#1376 and #1377 allow for plotting reference lines & areas along the x axis as well as documented examples
81reap commentedon Aug 23, 2026
seems like the linked resources have updated guidance
these could be warnings or rules we can capture in a warning system like #210 (comment)