[FR] Enable axis manipulation for matrix plots

[TorkelE]

I have the following matrix of colors:

using Plots
test = fill(RGB{Float64}(1,1,1),3,3);
test[1,1] = RGB{Float64}(0,0,0); test[1,2] = RGB{Float64}(0,0,0.5); test[1,3] = RGB{Float64}(0,0,1);
test[2,1] = RGB{Float64}(0.5,0,0); test[2,2] = RGB{Float64}(0.5,0,0.5); test[2,3] = RGB{Float64}(0.5,0,1);
test[3,1] = RGB{Float64}(1.0,0,0); test[3,2] = RGB{Float64}(1.0,0,0.5); test[3,3] = RGB{Float64}(1.0,0,1);
plot([1,2,3],[1,2,3],test)

This gives a plot like

Now imagine if I would want to flip the y-axis, so that the element [1,1] is in the bottom left corner. Intuitevely one would want to do so through

plot([1,2,3],[3,2,1],test)

this, however, gives a weird result:

Furthermore, say that I want a different scale of one axis, e.g.

plot([1,2,3],[0.1,0.2,0.3],test)

this also compresses that axis:

making the figure unreadable. It would be very useful to be able to re-scale the axis, without warping the figure itself.

All these tests are made using Plots 1.3.6.

[daschw]

The kwargs yflip = false for the first plot and aspect_ratio = :none for the last should handle this.

[TorkelE]

That worked wonders! Thanks a lot.