Easy question from a newbie

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Andrew
Andrew 2013-3-8
This should be a really easy question for some of you...I think.
Is there a function to specifically call out the number of rows in matrix? Length usually works but it takes the "longest side" so if you have more rows than columns, it counts the columns. I know size returns both the # of rows and columns, but I'm tweaking somebody else's more complicated code, so I just need a function to replace length where its reading # of columns instead of # of rows.
Thanks

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Azzi Abdelmalek
Azzi Abdelmalek 2013-3-8
编辑：Azzi Abdelmalek 2013-3-8
size(A,1) % number of rows
size(A,2) % number of columns
size(A,3) % number of channels

更多回答（3 个）

Image Analyst
Image Analyst 2013-3-8
编辑：Image Analyst 2013-3-8
Use the size() function:
theSize = size(yourArray);
theSize will be a list of all the dimension sizes in your array, however many there might be, for example [2,3,2,5,16] for a 5 dimensional array. If you just want the rows, which is the first dimension, you can do this:
numberOfRows = size(yourArray, 1);
If you wanted the number of columns, you'd specify 2 instead of 1, and so on.
Or if you know it's two dimensions:
[rows, columns] = size(yourArray);
Or if you know it's 3 dimensions, like a color image:
[rows, columns, numberOfColorChannels] = size(yourImageArray);
Ruben
Ruben 2013-3-8
you can use the size command for this. Just extract the first value of the output of the size command. For example:
A = rand(2,3)
temp = size(A)
rows = temp(1)
will return 2, this is the number of rows.
Ryan Livingston
Ryan Livingston 2013-3-8
I would just write a little function to do it:
function n = ncols(A)
s = size(A);
n = s(1);

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