How to get row and column from a vector size

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Houssam
Houssam 2021-6-18
评论： Houssam 2021-6-19
Hi matlab Community
i am back again with anouther question
i have a vector with variable length like this :
Vector = [10 20 30 40 50 60 70 80 9 100]
> numel(Vector) =
10
or
Vector = [ 1 2 3 4 5 ]
> numel(Vector) =
5
i want to reshape the vector to a matrix with the 2 largest row and coluumn.
but i can't find out how to go from vector size to matrix row and column
thanks in advance
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James Tursa
James Tursa 2021-6-18
What do you mean by "2 largest row and column"? Please give examples of reshaped results.
the cyclist
the cyclist 2021-6-18
Also, because 5 is a prime number, your example
Vector = [ 1 2 3 4 5 ];
cannot be shaped into a matrix (other than 1x5 or 5x1), so you might want to clarify that case as well.

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Scott MacKenzie
Scott MacKenzie 2021-6-18
编辑：Scott MacKenzie 2021-6-18
Assuming the vector length being a prime number (as noted by @the cyclist) is just one possible case of many, then the following code achieves the desired goal:
% test vector
v = rand(1,randi([1 100]));
n = length(v);
n1 = round(sqrt(n));
while n1 > 1
if ~rem(n,n1)
break;
end
n1 = n1 - 1;
end
n2 = n/n1;
fprintf('For %d elements, max matrix is %d x %d\n', n, n1, n2);
M = reshape(v, n1, n2); % reshaped vector
Output for some example runs:
For 18 elements, max matrix is 3 x 6
For 36 elements, max matrix is 6 x 6
For 44 elements, max matrix is 4 x 11
For 59 elements, max matrix is 1 x 59
  1 个评论
Houssam
Houssam 2021-6-19
thanks very mush, this exactly what i was looking for,
but there is always that problem of primary numbers!
so i've decided to to choose 512 as a number of columns
and add zeros at the end of the file so that it can be devided by that number of rows

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