Overlay multiple contours on a single plot

[timholy]

Feature description

In some cases, it's useful to be able to overlay contour lines of two functions on the same plot. For example, if you're solving a system of equations

f(x, y) = 0
g(x, y) = 0

for points x, y, it can build insight to overlay contour lines for both f and g on the same plot.

I've tried this:

fig, ax, hc = contour(f; labels=true, labelcolor=:red)   # f is a matrix of grid-values of one function
contour!(ax, g; labels=true, labelcolor=:blue)           # g likewise

but the outcome is clearly wrong: among other things, I see the f contour lines re-labeled in blue.

A partial work-around is to overlay two surface plots on the same Axis3, but one has to manage transparency etc. more carefully than for a contour plot.

For plot types, please add an image of how it should look like

From Numerical Recipes:

[lazarusA]

could you show us some more code for your functions? please. The following works as in the reference image:

using GLMakie
f(x, y) = abs(sin(x)* sin(y))
g(x, y) = abs(cos(x)* cos(y))

x = y = -3:0.1:3
zf = [f(x, y) for x in x, y in y]
zg = [g(x, y) for x in x, y in y]

fig = Figure()
ax = Axis(fig[1,1])
contour!(ax, x, y, zf; labels=true, color=:black, linestyle=:dash, linewidth=2,
    labelcolor=:red, levels = [0.5,1])
contour!(ax, x, y, zg; labels=true, color=:dodgerblue, linewidth=2,
    labelcolor=:blue, levels = [0.5,1])  
fig

[timholy]

Thanks! I don't have a record of my exact functions (they depended on a data set), but I'm guessing there must have been some degeneracy. I'll close this, with apologies for the noise.