CODEWITHSUNDEEP
octave
tsigo
tsigo

Reputation: 13

Problem with Octave. Can't recognize a matrix

I try to build a script on Octave and I receive this message:

error: script2: =: nonconformant arguments (op1 is 1x1, op2 is 1x10)
error: called from
    script2 at line 5 column 1

My script is:

l = 20:29;
m = 30;

for i = 0:9
  a(i + 1) = l / m;
end

Can someone help me fix this?

Upvotes: 1

Views: 95

Answers (2)

viking
viking

Reputation: 36

Since Octave is capable of doing matrix operations, you don't need the for loop in the first place.
I would rather write:

l = 20:29;
m = 30;
a = l / m;

This is much more efficient.

Upvotes: 1

Mad Physicist
Mad Physicist

Reputation: 114290

Octave allows you to assign to a non-existent name by making a scalar. You can then append to it by assigning to an index that is one past the length.

When you assign to a(1), a is created as a scalar (or 1x1 array). l / m is 1x10. That is what your error message is telling you.

There are a couple of workarounds. If you want to just accumulate the rows of a matrix, add a second dimension:

a(i + 1, :) = l / m;

If you want columns:

a(:, i + 1) = l / m;

The problem with this approach is that it reallocates the matrix at every iteration. The recommended approcach is to pre-allocate the matrix a and fill it in:

l = 20:29;
m = 30;
a = zeros(10);

for i = 1:10
  a(i + 1, :) = l / m;
end

Upvotes: 2

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