Polar contour plot

[psalvaggio]

Hi, I am trying to plot a bidrectional reflectance distribution function (BRDF) with this library. Traditionally, this is done as a filled contour plot in polar space. I have done this in the past with matplotlib, but I didn't see it in the gallery of examples. Is it possible in matplotplusplus? Thanks!

[alandefreitas]

The polar function returns a line_handle (a shared_ptr to a line)

matplotplusplus/source/matplot/core/axes_type.h

Line 1309 in 159a438

line_handle polarplot(const std::vector<double> &theta,

A line plot has a fill property

matplotplusplus/source/matplot/axes_objects/line.h

Line 77 in 159a438

class line &fill(bool fill);

that might give you what want if you set it to true. Something like:

auto h = ax->polar(...); // or matplot::polar(...)
// and then
h->fill(true);

But I haven't tested that yet but it should work, because polar histograms also use filled lines:

https://github.com/alandefreitas/matplotplusplus/blob/master/examples/polar_plots/polarhistogram/polarhistogram_1.cpp

[psalvaggio]

so looking at polarplot, it takes a 1D array of theta/rho values. I have more of a 2D dataset, with a set of zenith/azimuth (which map to r/theta), with a function value at each. The plot I'm trying to make looks like:

I think what I'm after is just a way to make contourf draw with polar axes instead. Is that possible?

[alandefreitas]

Mmmmm.... You might be able to achieve that with contourc then. Same as above (get handle, fill(true), etc...), but give the polar plot polygons for the contour lines instead. You can calculate the contour lines with contourc. (Still have never tested any of that though)

[psalvaggio]

OK, thanks. I will give it a try!