Error using sym/cat>checkDimensions CAT arguments dimensions not consistent.

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Jos van Weert
Jos van Weert 2023 年 3 月 6 日
コメント済み: Jos van Weert 2023 年 3 月 15 日
I have the following code (there is a space before the minus sign in the first equation):
eqns = [x -y==0;
x+y==0]
This generates the following series of messages:
Error using sym/cat>checkDimensions CAT arguments dimensions not consistent.
Error in sym/cat>catMany (line 33) [resz, ranges] = checkDimensions(sz,dim);
Error in sym/cat (line 25) ySym = catMany(dim, args);
Error in sym/vertcat (line 19) ySym = cat(1,args{:});
If I delete the space before the minus sign it works fine:
eqns = [x-y==0;
x+y==0]
Or a space behind the minus sign it also works fine:
eqns = [x - y==0;
x+y==0]
Why is it not allowed to use a space before the minus sign?

回答 (1 件)

Bhanu Prakash
Bhanu Prakash 2023 年 3 月 15 日
編集済み: Bhanu Prakash 2023 年 3 月 15 日
Hi Jos,
As per my understanding, you are trying to initialize a matrix containing linear equations but are facing some errors, when you tried to initialize them differently.
In the first case, where there is a space before the minus sign, both "x" and "-y==0" are identified as separate elements by the compiler. So, the compiler tries to create a row matrix using those two elements. But the second row has only one term i.e., "x+y==0", making the dimensions of the matrix inconsistent. This is leading to the error saying, "CAT arguments dimensions not consistent".
Please have a look at the code below, for your reference:
eqns=[x -y==0]
The output of the above code is mentioned below, which indicates a row matrix:
eqns =
[x, -y == 0]
In all other cases, the compiler considers "x-y==0" as a single element, thereby creating a column matrix having the elements "x-y==0" and "x+y==0".
You can access the documentaion for “Matrices and arrays” here:
Hope this answer helps you.
Thanks,
Bhanu Prakash.

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