How to write a for loop that creates a vector of [1:1000, 1001:2000,....,n]
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I am trying to write a loop that creates a vector with blocks of data. How exactly would the above be possible?
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Geoff Hayes
2020-2-13
by randomize the order of the results do you mean that rather than blocks of 1:1000, 1001:2000, etc. you want the 1:100000 randomly "distributed" across the 100 blocks?
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the cyclist
2020-2-13
% Define block size and number of blocks
blockSize = 1000;
numberBlocks = 50;
% Create vector of all values
A = 1:(blockSize*numberBlocks);
% Reshape into blocks
A = reshape(1:(blockSize*numberBlocks),blockSize,numberBlocks);
% Randomize the blocks
A = A(:,randperm(numberBlocks));
% Convert back to vector
A = A(:)';
Some of these steps could be combined, but I separated them for clarity.
I recommend testing this with a very small block size (maybe 3) and number of blocks (maybe 5) to verify it does what you want.
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Guillaume
2020-2-13
Another way to obtain the same:
blockSize = 1000;
numberBlocks = 50;
A = reshape((randperm(numberBlocks) - 1) * blockSize + (1:blockSize)', 1, [])
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Jon
2020-2-13
编辑:Jon
2020-2-13
Just to make Geoff's suggestion more concrete, suppose you had a length 100000 vector of data points. You could put this into a matrix with 2000 rows and 50 columns. Each column would be a "block" of data if this is what you mean. To do this just use
X = reshape(x,2000,50)
Note, I still don't really understand what you are trying to do, but just to match up a little closer to your description if the vector x in the above expression went from 1:100000 then the first column of X would have the numbers 1 up to 1000 the next column would have the number 1001 up to 2000 etc
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