Creating one array of columns from Matlab Meshgrid
I am working on an open source that needs to have a mesh file which is a 1D array. I am creating a grid via MESHGRID in Matlab and then using a FOR loop on the data column stack to create the file. It will take a very long time due to the FOR loop. Can anyone suggest me a better algorithm for this problem that will speed up my process. thank you in advance
clear all;
clc;
close all;
th = (0:0.5:360)*pi/180;
r = 0:0.2:1;
z = 5:.01:15;
[TH,R,Z] = meshgrid(th,r,z);
[X,Y,Z1] = pol2cart(TH,R,Z);
L1 = length(X(:,1,1))
L2 = length(Y(1,:,1))
L3 = length(Z1(1,1,:))
T = 1;
for i = 1:1:L1
for j = 1:1:L2
for k = 1:1:L3
M(T,1) = X(i,j,k) ;
M(T,2) = Y(i,j,k) ;
M(T,3) = Z1(i,j,k) ;
T = T+1
end
end
end
dlmwrite('hpts.in',M,'precision','%2.2f','delimiter',' ','-append');
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It is not simple:
M = [X(:), Y(:), Z1(:)]
Although to get technically the same result, you first calculate by the third dimension, when the Matlab methods (:)
are the primary columns, that is, they go by size 1 first, so you need to reorder the dimensions, so use permute
either (:)
or reshape
. With help, reshape
you can use the anonymous function neatly:
columize = @(A)reshape(permute(A, [3,2,1]), [],1,1)
M = [columize(X), columize(Y), columize(Z1)]
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hacked into pol2cart.m
and used a custom version meshgrid
to achieve the desired result with this code -
%// Inputs th = (0:0.5:360)*pi/180; r = 0:0.2:1; z = 5:.01:15; %// Start processing Mcol1 = cos(th)'*r; %//' Mcol1 = repmat(Mcol1(:).',numel(z),1); %//' Mcol2 = sin(th)'*r; %//' Mcol2 = repmat(Mcol2(:).',numel(z),1); %//' M = [Mcol1(:) Mcol2(:) repmat(z(:),numel(r)*numel(th),1)]; dlmwrite('hpts.in',M,'precision','%2.2f','delimiter',' ','-append');
It seems to be about faster than the code you would get with pre-distribution on my system. 6x
M
Alternatively, you can store the transposition th
into a variable and use it in two places where those transposition values are used - cos(th)'
and sin(th)'
so this should speed it up.
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