Is there any way to represent symbolic variables as I write from left to right?

As you know in Matrix manipulation you're not allowed to change the order of Matrix. for example AB # BA (the commulative law is usually broken).

I was wondering if there was a way to represent the below matrix multiplication?

How can I modify this simple code to output the correct matrix ruls? ie change (BC/A) to (C/A)*B

syms I  A B C D 
sympref('MatrixWithSquareBrackets',true);
E=[1 0 ; -C/A 1] 

E = 

F=[A B ; C D]

F = 

X=E*F

X = 

Thanks a bunch!

[Torsten]

https://de.mathworks.com/matlabcentral/answers/766691-preserve-the-order-of-matrix-when-doing-symbolic-matrix-multiplication

Answer 1

[Paul]

Since R2021a, one can define symbolic matrices. I haven't really used them too much and so don't know how to get any further than what is shown below. I'm surprised Matlab won't carry out the multiplication of the block matrices. Maybe there is another command that will do so.

syms I [2 2] matrix
syms A [2 2] matrix
syms B [2 2] matrix
syms C [2 2] matrix
syms D [2 2] matrix
E = [I zeros(2);-C*inv(A) I]

E = 

F = [A B;C D]

F = 

G = E*F

G = 

[Ahmad]

Thank you dear Paul, You stated the related MATLAB symbolic commands well.

Now how can I see the result of block-matrix multiplication G=E*F?

[Walter Roberson]

symmatrix2sym()

[Ahmad]

Dear Walter, I mean how can output G1 to as seen in G2 in matrix closed form.

syms I A B C D Z [2 2] matrix
Z=0*Z

Z = 

I=I/I

I = 

E = [I Z;-C/A I];
F = [A B;C D];
G1 = E*F

G1 = 

manually created the output: this is not the case...

G2=[A  B; Z D-C/A*B]

G2 = 

=

[Walter Roberson]

You cannot. Block operations like that are not supported.

Perhaps I should not say "cannot", but rather "no method is provided". There might hypothetically be some way involving using mapSymType or similar operations.

[Paul]

That's too bad that block matrix multiplication isn't supported. Maybe that's coming in a future release.

It would also be cool if the identity matrix and the zero matrix could be created as special symmatrix constants with specified dimensions to be used in equations such as above.