how do you define a matrix and its variable

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Wenchen Liu
Wenchen Liu 2021-11-15
评论： Adam Danz 2021-11-15
I want to create a matrix , by i * j, in matlab, and then let matlab run this. I need to tell matlab what is i and what is j before i define the matrix, right? Then when I define the matrix, can I write aMatrix = [i, j]?
I know how to do matrix like: aMatrix = [1 3 7 ; 5 6 7], but now I want to know how to make a general matrix by giving i and j in matlab.

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回答（1 个）

Adam Danz
Adam Danz 2021-11-15
编辑：Adam Danz 2021-11-15
Ran in:
Learn about preallocation.
Options:
i = 4;
j = 3;
M = nan(i,j)
M = 4×3
NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN
M = ones(i,j)
M = 4×3
1 1 1 1 1 1 1 1 1 1 1 1
M = zeros(i,j)
M = 4×3
0 0 0 0 0 0 0 0 0 0 0 0
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Wenchen Liu
Wenchen Liu 2021-11-15
but how could I define i？and should I define it before a and b?

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