Hi! I’m trying to create a simple heatmap with a logarithmic colorscale. The documentation for dtick in coloraxis says: If the axis type is “log”, then ticks are set every 10^(n"dtick) where n is the tick number. For example, to set a tick mark at 1, 10, 100, 1000, … set dtick to 1. I can’t get…

I was one of those who had the problem :slightly_smiling_face: I no longer work on that project but my recollection is that we ended up having to create a custom color bar with more ticks so that the bar looked OK for a logarithmic range. Not exactly ideal but it was hoped that a new version of plo…

Thanks for your response naskew! Yeah, that’s also my workaround I was thinking of. There is Logarithmic Color scale with Graph Objects , which shows how to change colors in a logarithmic way. However, the distribution on the colorbar is still linear. It really seems, a logarithmic colorbar is just…

For reference: I created GitHub issue #7376 for the problem.

Thanks @Saratoga , for you feedback! However, your example doesn’t really use a logarithmic colorscale, but only labels it similar to a logarithmic scale, i.e. “100”, “1000”, “10k”, etc. In a real logarithmic scale, the distances between all these labels would be equal, which is not the case. And th…

Wow, that’s nice! Many thanks! It seems this is what I need. I have to check it out in more details, but looks good. A minor drawback I see is, the actual z-values have to be translated before passing to Plotly and thus the tooltips have to use customdata to show correct values. Anyway, I think I …

Logarithmic coloraxis in heatmaps not working as documented

plotly.js

Saratoga February 24, 2025, 7:08pm 5

Check this out, the first heatmap is an example that I took from the Python documentation and passed it to javascript and in the second I just adapted your data to the first example.

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Logarithmic coloraxis in heatmaps not working as documented

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