# Polar contour plot

Hi,

A simple question: how to create a polar contour plot? Just like this one (I randomly grabbed from google):

I've seen people combine an image plot with a polar plot in Igor to do this.

The tricky part is generating the image, and that depends on what form your data is in.

The trick is to create a rectangular image and then set the parts outside of the circle to NaN (transparent).

--Jim Prouty
Software Engineer, WaveMetrics, Inc.

Although not very perfect, but I kind of nailed this problem. Just simply convert the data (which are supposed to plot into polar graph and do the contour thing) into xy coordinate system, then use the contour function. Of course in they way the contour graph (img) is "rectangular", and we would have to cut out the edge and make it look like "circular" as if it were in a polar coordinate system (just like you mentioned). A demo is shown here.
[img]20. Windrose.png[/img]

I know it's ugly, and to be honest, it looks a little bit weird. This is probably because the igor contour function is originally designed for making figures in xy coordinate system. If it were "projected" onto a polar coordinate system, it may look deformed.

Nevertheless, it's better than nothing, and pretty simple :)

JimProuty wrote:
I've seen people combine an image plot with a polar plot in Igor to do this.

The tricky part is generating the image, and that depends on what form your data is in.

The trick is to create a rectangular image and then set the parts outside of the circle to NaN (transparent).

--Jim Prouty
Software Engineer, WaveMetrics, Inc.

20. Windrose.png (140.66 KB)
You can hide the ragged edge by allowing the radius=5 axis circle to be drawn (over it).

--Jim Prouty
Software Engineer, WaveMetrics, Inc.