Creating vector of symbols
33 views (last 30 days)
Show older comments
For example, A = sym('A%d%d', [3 3]) generates the 3-by-3 symbolic matrix A with the elements A11, A12, ..., A33
0 Comments
Accepted Answer
Walter Roberson
on 4 Mar 2011
Edited: Walter Roberson
on 22 Feb 2017
For example, for a P x Q x R matrix,
[x,y,z]=ndgrid(1:P,1:Q,1:R);
A = sym( reshape( ...
cellfun(@sym, ...
strcat('A', ...
cellstr(num2str(x(:))), ...
cellstr(num2str(y(:))), ...
cellstr(num2str(z(:)))), ...
'Uniform', 0), ...
P, Q, R ) );
The code is not as long as it looks; I formatted it for display purposes.
Trim to two dimensions or expand to the number of dimensions needed.
4 Comments
Karan Gill
on 2 Mar 2017
No, >2 dim works in R2016a (unless I misunderstand you).
>> A = sym('A', [2 2 2])
A(:,:,1) =
[ A1_1_1, A1_2_1]
[ A2_1_1, A2_2_1]
A(:,:,2) =
[ A1_1_2, A1_2_2]
[ A2_1_2, A2_2_2]
Walter Roberson
on 2 Mar 2017
Ah, then I think that advance is best left as a comment rather than by editing the response which was appropriate for the time it was written and continues to be required by people using older versions.
More Answers (3)
Brian
on 4 Mar 2011
3 Comments
Walter Roberson
on 4 Mar 2011
It does appear that supplying a size is a new feature as of 2010b; the 2010a documentation does not show it.
http://www.mathworks.com/help/releases/R2010a/toolbox/symbolic/sym.html
Paulo Silva
on 4 Mar 2011
A=[3 3]; %create any numeric vector or matrix
A=sym(A) %convert it to symbolic
A=double(A) %convert it back to numeric (double in this case)
2 Comments
Paulo Silva
on 4 Mar 2011
One thing you should always have open in your matlab is the Workspace window so you can see what variables are create and their details, other ways is to do
class(A) or in the case of your small code class(ans).
In a way they can, that small code of yours gives the ans=2 but it's a symbolic response not numeric. My1=sym('1'); 2*My1 gives ans=2, again it's a symbolic value. There are other ways to make symbolic values but you should look first in your documentation.
See Also
Categories
Find more on Assumptions in Help Center and File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!