Contour plot with all lines in one color

[tomasaschan]

I tried this:

xs = 1:10.
ys = 1:10.
zs = Float64[x^2*log(y) for x in xs, y in ys]
plot(x=xs, y=ys, z=zs, Geom.contour, Scale.discrete_color_manual("gray"))

but the only difference between with and without the Scale element is that with it, it seems that the colors are chosen as distinguishable, while without it they are from a spectrum corresponding to the function value.

Is there a way to get all the contour lines in a contour plot in the same color?

[tomasaschan]

For reference, I realized this might be better suited for julia-users, and cross-posted it. If I get an answer there I'll be sure to post it here too.

[darwindarak]

This is probably not the best way to do this, but

plot(x=xs, y=ys, z=zs, Geom.contour, Scale.ContinuousColorScale(x->color("gray")))

seems to do what you want.

[dcjones]

Darwin's solution was pretty much to only way to do this, so I added a Scale.color_none which does what you want: suppress the default color scale.

[tomasaschan]

Thanks, both @darwindarak and @dcjones for quick response. As it turns out, I'm using this in a layered plot where I have both a layer with contour levels (which I want all grey) and a few other layers with 2D trace plots, for which I have a defined, manual color key. Since Scale objects can't be applied to layers, I don't know how to apply the fixes you've provided to this use case.

Here's an example plot command of what I'm trying to do:

plot(
    layer(x=xwall, y=ywall, Geom.path, Theme(default_color=color("black"))),
    layer(x=trace1x, y=trace1y, color=["Trace 1" for _ in trace1x], Geom.path),
    layer(x=trace2x, y=trace2y, color=["Trace 2" for _ in trace2x], Geom.path),
    layer(x=xfield, y=yfield, z=zfield, Geom.contour, #= What to put here, to make contours gray? =#),
    Scale.discrete_color_manual("blue","green"),
    Guide.colorkey("Traces"),
    Guide.xticks(orientation=:horizontal)
)

I tried adding a color argument to the contour layer as well (with color=["psi" for x in xfield, y in yfield]) but it borked on me (``discretize_make_pda has no method matching discretize_make_pda(::Array{ASCIIString,2}, ::Array{ASCIIString,1})).

Is there any way to accomplish this?

[dcjones]

Oh, this is trickier than I thought. Maybe the most natural thing to do would be to add a color argument to Stat.contour and Geom.contour, so you could say Geom.contour(color="psi") and have all the contours colored by one factor.

[tomasaschan]

Couldn't Geom.contour just respect the default color of the theme? If I want to change the color of something plotted with e.g. Geom.path I'd add an argument Theme(default_color=color("gray")) to the layer or plot invocation, so I think it would be the most intuitive if that applied to contours as well.

[protogeezer]

Since this is still open, here's a tiny bit of code that will "manually" add contours to a plot (p). If a complete example is needed, let me know.

p = plot whatever goes under the contours.
c = contours(x_range,y_range,M,8);
for i = 1:length(c)
for j = 1:length(c[i].lines)
curr_x,curr_y = coordinates(c[i].lines[j])
l = layer(x=curr_x,y=curr_y,Geom.line(preserve_order=true),
Theme(default_color=RGB(.2,.2,.2),line_width=.4mm));
unshift!(p.layers,l[1]);
end
end
display(p)