contour plot in polar system

[Tim Franke]

Hi,

I have a set of data in the following form:

r1 phi1 f1
r2 phi2 f2
r3 phi3 f3

where r and phi are the polar coordinates
and f is the value at that point.

Is it possible to create a plot with gnuplot that
is a circle and the circle is colored depending
on the value f at each region within the circle ?

Regards,

Tim

[Hans-Bernhard Broeker]

Tim Franke <tim_f...@gmx.de> wrote:

> Is it possible to create a plot with gnuplot that
> is a circle and the circle is colored depending
> on the value f at each region within the circle ?

The relation between your datafile and the plot you want is far too
indirect for that.

1) what is supposed to be done with the radius values you have?
2) are the phi values sorted? If so, how (sorting a circular variable into
a linear order isn't well-defined)
3) *how* is that color supposed to "depend on" f?

--
Hans-Bernhard Broeker (bro...@physik.rwth-aachen.de)
Even if all the snow were burnt, ashes would remain.

[Tim Franke]

Hello Hans-Bernhard,

I probably did not explain my problem clear. So I will explain more
detailed.

My radial coordiante r is 0.1,0.2 .... , 1.0
My phi coordinate is 5,10,15, ...., 360

At every combination of r and phi I have a function value f.

I want to visualize this data in that way, that I get a colored contour plot
of f. The area in which f is defined is a circle area. And I want this
circle to be filled with different colors depending on the value of f.
(e.g. High values of f means red color, low values means blue color
and inbetween there's the rest of the spectral colors.

Best regards,

Tim

[Hans-Bernhard Broeker]

Tim Franke <tim_f...@gmx.de> wrote:

> I want to visualize this data in that way, that I get a colored contour plot
> of f.

This is where it breaks down: gnuplot doesn't do colour-filled
contours yet. Not even in the development version. We have contours
in all versions, and color-mapped plots in the developement version,
but no colour-filled contours.

You can get a contour plot, but it will either have a visible seam at
phi=0 / 360 degrees, or it won't be circular --- you choose. The
contouring algorithm doesn't handle cylindrical coordinates, AFAIK,
which is why you must choose between these two evils. A rough outline
of a plot script could be

set mapping cylindrical
set contours base
set view 0,0
set nosurface
splot 'file' using 2:1:3

[hass...@gmail.com]

Hello Tim

Were you able to get this plot that you wanted? (contour plot in polar system) I have not been successful yet. (I am not interested in the color part, just the contours). thanks

- Adil