Retrieving a random element from each row in a matrix
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hi everyone
I have a 20 by 10 matrix. I am running the following code to retrieve a random element from each row of the matrix. In this case, I need to create a 20 by 1 matrix at the end. I have written the following code but it does give me a shuffle of the first column alone.
sz=size(R,1);
B=zeros(sz,1);
i=1:20
% for n=1:100
for j=1
for i=1:20
for row=1:20
M(i,j)=randi(length(R),20,1);
B(i,j)=R(M(i,j));
end
end
end
% end
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Star Strider
2019-5-23
It is likely easier to use the sub2ind funciton to create linear indices into ‘R’ from a defined list of random column subscripts:
R=randi(1000,20,10);
idx = sub2ind(size(R), (1:size(R,1))', randi(size(R,2),size(R,1),1));
B = R(idx)
The second argument defines the row indices and the third defines the random column indices.
See if that does what you want.
13 个评论
Star Strider
2019-5-24
As always, my pleasure.
The output of the randi function is uniformly distributed, not normally distributed. If you were to use the normal distribution instead (the randn function being one such), and you did not change the mean and standard deviation to create the ‘R’ matrix, the data would remain normally distributed.
If you do not otherwise change the parameters of the distribution you are using to create the matrix, the matrix should retain the properties of that distribution, regardless of how you sample it.
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