Matrix dimensions must agree when using .*

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Amy Phan
Amy Phan 2017-5-21
评论： Niladri Halder 2022-8-9
Hi all,
I've been trying to multiply two matrices together and I can not find where I went wrong. I'm trying to multiply the matrix and it's transpose together however I am getting the error, "Matrix dimensions must agree."
The two matrices contain the following information:
Name Size Bytes Class Attributes
D_tranpose 6x16384 98304 uint8
D 16384x6 98304 uint8
Does anyone have any ideas? Thanks in advance
  2 个评论
Niladri Halder
Niladri Halder 2022-8-9
nn2_p = nn2{nImage}.*mask_s;
Matrix dimensions must agree.
Please Help. Thank you.

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Walter Roberson
Walter Roberson 2017-5-21
C = A.*B is element-by-element multiplication, for which unless one of A or B is a scalar, the result C(J,K) = A(J,K).*B(J,K) . For that to work, the matrices must be the same size.
Perhaps you want D_tranpose * D which would be algebraic matrix multiplication, and would give you a 6 x 6 result for those matrices.
  2 个评论
Amy Phan
Amy Phan 2017-5-22
Thank you so much for your reply. When I try and compute D_tranpose * D I receive another error saying:
Error using *
MTIMES is not fully supported for integer classes. At least one input must be scalar.
To compute elementwise TIMES, use TIMES (.*) instead.
Walter Roberson
Walter Roberson 2017-5-22
double(D_tranpose) * double(D)
When you do algebraic matrix multiplication involving uint8 the result is quite likely to exceed the capacity of uint8, so you would not want to use * directly between uint8 even if it were permitted.

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