How can I create a polar plot from 2d matrix

Hi all, I have measured the thickness of the liquid around the pipe at different angles (60 measurement points circumferentially). Therefore I have 60x1 matrix. My question is: how can I draw a polar plot showing the variation of the thickness around the pipe (at 60 points). The pipe diameter is 125 mm and we are only interested in drawing the thickness variations around the wall of the pipe. Any suggestions please? Regards

Answer 1

[Star Strider]

I don’t have your data, so I cannot experiment with it. If you have it in angle and radius units, you can use the polar plot function, or to plot it in Cartesian coordinates, the pol2cart function to convert it first.

[Star Strider]

abu’s ‘Answer’ moved here:

Many thanks Star Strider for your reply. in fact I have only average values as shown below. these 60 points are measured around 150 mm diameter pipe and they are equally spaced. I want to draw a full circule with a diameter of 150 mm first and inside that circule I want to draw a variation of thickness at different angles (i.e. the measured 60 points).

0.033084658 0.293907372 0.653043915 0.618103773 0.703585776 0.777590126 0.825294609 0.528666785 0.688760918 0.872587373 0.657859085 0.717440963 0.805964633 0.725771482 0.587454046 0.566766564 0.961635713 0.847234819 0.811701097 0.776176029 1.08926567 0.949577508 0.825740278 0.873275014 0.888530172 0.849409288 0.673467813 0.77972922 0.81886664 0.808809879 0.816000148 0.931310678 0.615656008 0.576548781 0.446879004 0.438324301 0.640064898 0.601247486 0.551295579 0.516556439 0.589850362 0.956059382 0.822712949 0.761515398 0.7090789 1.193686078 0.88253056 0.9139452 0.641509173 0.562850056 0.440092106 0.573124828 0.607873098 0.642840251 0.611243867 0.551509593 0.505016326 0.594895412 0.603441052 0.477979195

[Star Strider]

I would use polar (or polarplot if you have R2016a or later) to do this:

r = [0.033084658
    0.293907372
    0.653043915
    0.618103773
    0.703585776
    0.777590126
    0.825294609
    0.528666785
    0.688760918
    0.872587373
    0.657859085
    0.717440963
    0.805964633
    0.725771482
    0.587454046
    0.566766564
    0.961635713
    0.847234819
    0.811701097
    0.776176029
    1.08926567
    0.949577508
    0.825740278
    0.873275014
    0.888530172
    0.849409288
    0.673467813
    0.77972922
    0.81886664
    0.808809879
    0.816000148
    0.931310678
    0.615656008
    0.576548781
    0.446879004
    0.438324301
    0.640064898
    0.601247486
    0.551295579
    0.516556439
    0.589850362
    0.956059382
    0.822712949
    0.761515398
    0.7090789
    1.193686078
    0.88253056
    0.9139452
    0.641509173
    0.562850056
    0.440092106
    0.573124828
    0.607873098
    0.642840251
    0.611243867
    0.551509593
    0.505016326
    0.594895412
    0.603441052
    0.477979195];

a = linspace(0, 2*pi, size(r,1))';                      % Create Angle Vector

figure(1)
polar(a, r)                                             % Plot Variation Only

figure(2)
polarplot(a, [ones(size(r))*125, r+125])                % Plot Radius & Variation

[abu]

Many thanks Star Strider. your answer was really helpful. one more thing, suppose I have film thickness data and its associated angles with time (frame) variations. in other words, I have 3d matrix. is it possible to animate the polar plot with time to see how the film thickness changes with time as animation??

for simplicity, let's say that we have 4x1x5. therefore, we have 5 frame (each frame is separated by 0.02 second) and at each frame we have 4 values of film thickness taken at 0, 90 180 and 270 deg).

The data is given below;

frame 1:

0.293907372

0.653043915

0.618103773

0.703585776

frame 2

0.777590126

0.825294609

0.528666785

0.688760918

frame 3:

0.872587373

0.657859085

0.717440963

0.805964633

frame4:

0.725771482

0.587454046

0.566766564

0.961635713

frame 5:

0.847234819

0.811701097

0.776176029

1.08926567

[Star Strider]

My pleasure.

I never tried this with a polar or polarplot function. You would need to use the drawnow and refreshdata functions, paging through the third dimension of your matrix for each plot. (I just used two profiles to illustrate the idea. Make the appropriate changes to the code to plot the full profiles.)

Another option is to plot all your data together in one plot.

Both options:

Frames(:,1) = [0.293907372
               0.653043915
               0.618103773
               0.703585776];

Frames(:,2) = [0.777590126
               0.825294609
               0.528666785
               0.688760918];

a = [0; 90; 180; 270]*pi/180;

figure(1)                                       % Animated Plot
for k1 = 1:size(Frames,2)
    polarplot(a, Frames(:,k1)+125)
    drawnow
    refreshdata
    pause(1)                                    % Optional 
end

figure(2)
polarplot(a, Frames+125)                        % All Data Plotted Together

Note: There are very small differences with repsect to a very large radius, so there is not much of a visible change between the sections here.

[Star Strider]

abu’s ‘Answer’ moved here:

Thank you. I have tried your code, but I got the following error;

Undefined function or variable 'polarplot'. the version I used is 2015.

any suggestion!

[Star Strider]

Yes. Substitute polar for polarplot in figure(1).

Without polarplot, you will not be able to plot all of your vectors in the same call, so the code for figure(2) changes to:

figure(2)
polar(a, Frames(:,1)+125)
hold on
for k1 = 2:size(Frames,2)
    polar(a, Frames(:,k1)+125)
end
hold off

Answer 2

[abu]

I used polar function and it works. many thanks

[Star Strider]

My pleasure.