use pol2cart with not equal arguments

2014 9 9
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更新时间：2014 9 10
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Hello all
Is it possible to use the pol2cart(THETA,RHO,Z) command if the vectors THETA and RHO are not equally sized and, as a result, matrix Z is not square? In my calculations, the THETA vector has 100 elements and the RHO vector has 1024 elements (so Z is 1024x100). If I increase the elements of THETA, then my program will take too long to finish (almost 8 days!).
Any help would be appreciated! Thank you all!
Antigoni

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Sean de Wolski
Sean de Wolski 2014-9-9

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tic
[rr, thth] = meshgrid(1:100,1:1024);
[x,y] = pol2cart(rr,thth);
toc
Taking a few thousanths of a second on my laptop.

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the cyclist
the cyclist 2014-9-9

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theta = rand(1024,100);
rho = rand(1024,100);
z = rand(1024,100);
tic; [X,Y,Z] = pol2cart(theta,rho,z); toc
Elapsed time is 0.005789 seconds.
I guess I'm confused on what you are trying to do that takes so long.
Also, I am guessing that the meshgrid() function might be handy for you to convert theta and rho vectors into what you need for this.
Antigoni
Antigoni 2014-9-9

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Thank you all for your replies. I didn't mention that my source code is in fortran and only the results' post-processing is made in Matlab.
Briefly, my problem is to simulate the wave propagation in a plate on the x-y plane. For that reason, I solve my equations for various values of x and at different angles. If I use 1024 values of x (which is OK for my resolution) and the same values for angle (since the THETA and RHO must be equally sized), then the Fortran code takes too long. So, now I will try your suggestions in my post-processing.
Though, I have one more question. My input THETA and RHO are vectors of dimensions (1,100) and (1,1024) respectively. In order to use your solutions, I should convert them to matrices, by simply copying and pasting the row as many times as the desired dimensions are reached, right?

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Sean de Wolski
Sean de Wolski 2014-9-9
Replace my inputs to meshgrid with rho and theta
[rr,thth] = meshgrid(RHO,THETA)
Antigoni
Antigoni 2014-9-9
OK, I think I get this (I didn't know this command, I'm sorry). The output matrices X and Y from pol2cart are created in the same manner? Meaning, the rows and columns of X, Y are also copies of a vector?
Sean de Wolski
Sean de Wolski 2014-9-9
exactly! Look at a small example:
[xx,yy] = meshgrid(1:3,1:4)
Antigoni
Antigoni 2014-9-9
Thank you so much! I will try it in a while and I'll come back later.
Antigoni
Antigoni 2014-9-10
Well Sean de Wolski, I tried your solution and it works perfectly! Thanks again for your help!

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