scatter polar plot interpolation

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tony74
tony74 on 6 Feb 2019
Commented: yaopeng on 23 Dec 2020
How can I produce a scatter plot in polar coordinates in Matlab? I need to have a scatter plot (r,theta,Z) where Z values are represented with a colorbar.
The result which I would like to obtain is the same of polarPlot function in R (openair package). In the image you can see an example of graph obtained
with R.
R_WDS_NO3_emission.png
In Matlab I tried with ScatterWindRose (from File Exchange) function, but it is not exactly what I want. I need a kind of surface interpolation of the dots.
screenshot scatter plot.jpg
Can you help me?

Accepted Answer

Bjorn Gustavsson
Bjorn Gustavsson on 6 Feb 2019
Have a look at the help for TriScatteredInterp, griddata those functions should help you interpolate between your measurement points, then you might have use for this file exchange contribution: Polar pcolor
HTH
  4 Comments
tony74
tony74 on 12 Feb 2019
Sorry, but I having errors, yet.
This is the code used, following your suggestions:
theta_i = linspace(0,2*pi,361);
mediau_i = linspace(0,1,length(mediau));
[mediau_i,theta_i] = meshgrid(mediau_i,theta_i);
mediaA_F1 = scatteredInterpolant(mediau,tetanord,media_a1);
mediaA_F2 = scatteredInterpolant(mediau.*cos(tetanord),...
mediau.*sin(tetanord),...
media_a1);
media_Ai1 = mediaA_F1(mediau_i,theta_i);
media_Ai2 = mediaA_F2(mediau_i.*cos(theta_i),mediau_i.*sin(theta_i));
[h,c]=polarPcolor(mediau(:,1),tetanord(:,1)'*180/pi,media_Ai1);
and this is the error message:
Size of Z is : [361 42384]
Size of R is : [42384 1]
Size of theta is : [1 42384]
Error using polarPcolor (line 80)
dimension of Z does not agree with dimension of R and Theta
Bjorn Gustavsson
Bjorn Gustavsson on 12 Feb 2019
Try to find out why! Step 1, go trhough all possible permutations of Z R and theta.
Step 2: type "dbstop if error" on the command-line prompt, run the polarPcolor again - and you'll get a debug-prompt in the function where the error occurred, then you have command-line access to all variables in that workspace - as well as the possibility to jump further up (and down) the function-call-stack by "dbup" (and dbdown).
HTH

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