MATLAB: Substitute string to double

doubleMATLABreplacestringsymbolicSymbolic Math Toolbox

Hi everyone, very simple question here:
I have this:
Acell =
  3×3 cell array
    '0+1/R1'    '0-1/R1'         '1'
    '0-1/R1'    '0+1/R1+1/R2'    '0'
    '1'         '0'              '0'
Apart from that, I have this:
R1 = '1000'; 
R2 = '1000';
My goal is to convert the original string to a double array so I could perform calculations afterwards, like this:
A = [ 1/1000 -1/1000 1; -1/1000 1/1000+1/1000 0; 1 0 0;];
What I tried so far was:
Acell = strrep(Acell,'R1','1000');
Acell = strrep(Acell,'R2','1000');
A = str2double(Acell);
Obtaining:
A =
   NaN   NaN     1
   NaN   NaN     0
     1     0     0
Any thoughts? This is just a little example, my idea is doing that job for much more elements so I'm not sure about using 'strrep' too.
Many thanks in advance

Best Answer

>> A = {'0+1/R1','0-1/R1','1';'0-1/R1','0+1/R1+1/R2','0';'1','0','0'};
>> A = strrep(A,'R1','1000');
>> A = strrep(A,'R2','1000');
>> B = cellfun(@str2num,A)
B =
    0.0010   -0.0010    1.0000
   -0.0010    0.0020         0
    1.0000         0         0
Warning: will run arbitrary commands, use at your own risk!
Rather than storing functions as strings, perhaps they should be stored as function handles. Then you can simply and effiiciently call them with the required input data (as numeric, of course!).
>> A = {'0+1/R1','0-1/R1','1';'0-1/R1','0+1/R1+1/R2','0';'1','0','0'};
>> F = cellfun(@(s)str2func(['@(R1,R2)',s,';']),A,'uni',0); % convert to function handle
>> B = cellfun(@(f)f(1000,1000),F) % call all with the same inputs
B =
    0.0010   -0.0010    1.0000
   -0.0010    0.0020         0
    1.0000         0         0
>> F{1,2}(20,30) % call function {1,2}
ans =
   -0.0500
Related Question