option to flip heatmap

[ssfrr]

currently heatmap puts cell (1,1) in the top-left corner. This is often what you want (like when visualizing an image), but other times you want it on the bottom-left (e.g. in an audio spectrogram).

for reference PyPlot's imshow function takes the origin="upper" or origin="lower" options.

[mkborregaard]

The Plots syntax is yflip = true

[ssfrr]

I find that less clear - you have to know what the default is to understand what yflip will do

[mkborregaard]

It's also a lot more general - it's not restricted to heatmaps, which is just another seriestype for plot, rather than some specific plotting function with bespoke arguments to learn. The y axis has the lowest value in the bottom on all plots, so there's nothing to remember. If you want the y axis to have the lowest value on top, you use yflip = true. It's also not restricted to the y axis, you can xflip and zflip as well (they of course also by default have the lowest values at the origin).

That's the key point of Plots and I believe a central component of its success: generality.

(That said it would be easy to have the flip keywords accept :origin_top and :origin_bottom arguments as well for those who'd like that - accepting both Bool and Symbol is a classic strategy in Plots for clarity)

[ssfrr]

Yeah, if the convention is that the origin is in the lower-left for everything than I can see how yflip is good and consistent. In that case the default for heatmap should be flipped from what it is now (the origin is currently in the top-left), and `yflip=true would flip it back, right?

[mkborregaard]

Yes 👍

[SimonDanisch]

I'm planning to have each visual be accompanied by a rich transformation attribute - which will support padding, placement, flipping and maybe even arbitrary transformation functions, if I figure opengl transpilation out fast enough.
This will get implemented for all plotting types and it will be possible to inherit those from the parent scene (so that you can transform the whole scene).

[mkborregaard]

That sounds awesome.

[asinghvi17]

scale! should do this.

[xaviergonzalez]

Wait so how do we actually flip the y-axis for a heatmap in Makie?

[jkrumbiegel]

ax.yreversed = true

[xaviergonzalez]

ax.yreversed = true

But what if I'm not using an ax atttribute, i.e. I'm just doing something like

CairoMakie.heatmap(mat, yflip=true)

This code produces the heatmap, just not with the y-axis flipped.

[asinghvi17]

You would have to do CairoMakie.heatmap(mat, axis = (yflip=true,)).

[jkrumbiegel]

It's yreversed if I'm not wrong