Perform operation on character arrays

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MarshallSc
MarshallSc on 12 Jul 2021
Commented: MarshallSc on 16 Jul 2021
How can I perform some operations on character cells? For example, after an if statement for a numeric cell array, I get another cell array that has characters instead of numeric values, for instance:
A{1,1}=[a,b,c;a,b,c;a,b,c]
A{1,1} corresponds to a cell array that has numerical values and I want to perform some operations for only the components of the numeric cell array that has "b"s not "a"s and "c"s in the character array.
For example, the original A{1,1} is:
A{1,1}=[1,2,3;4,5,6;7,8,9]
So I want to do some calculations for (2,5 and 8) only. My original cell array in large and I cannot select the positions of all "b"s individually and have to select them in a for loop automatically, so my question is how can I identify the index of these components and performsome some operation on them? Is this even possible?
  3 Comments
Christopher McCausland
Christopher McCausland on 15 Jul 2021
No problem Marshall,
Sorry I didn't have more time to provide a fuller answer though I see Walter has it covered very well! 'find' and 'ismember' are great for char and table manipulation and can be really powerful in these kind of situations.
Christopher

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Accepted Answer

Walter Roberson
Walter Roberson on 12 Jul 2021
Example
C = {'a','b','c';'a','b','c';'a','b','c'}
C = 3×3 cell array
{'a'} {'b'} {'c'} {'a'} {'b'} {'c'} {'a'} {'b'} {'c'}
A{1,1} = [1,2,3;4,5,6;7,8,9];
A{1,2} = randi(9, 3, 3);
A{1,3} = randi(9, 3, 3);
celldisp(A)
A{1} = 1 2 3 4 5 6 7 8 9 A{2} = 8 4 8 2 2 4 1 7 9 A{3} = 1 8 3 9 8 1 2 3 3
mask = ismember(C, 'b')
mask = 3×3 logical array
0 1 0 0 1 0 0 1 0
%maybe you want to select only those values into separate arrays
selected_values = cellfun(@(c) c(mask), A, 'uniform', 0)
selected_values = 1×3 cell array
{3×1 double} {3×1 double} {3×1 double}
%maybe you want to sum the corresponding selected values
selected_sum = sum(cell2mat(selected_values),2)
selected_sum = 3×1
14 15 18
%maybe you want to multiply the selected values by something, leaving the
%rest untouched
times_N = randi(9)
times_N = 6
selected_multiplied = cellfun(@(c) c.*~mask + times_N.*c.*mask, A, 'uniform', 0)
selected_multiplied = 1×3 cell array
{3×3 double} {3×3 double} {3×3 double}
celldisp(selected_multiplied)
selected_multiplied{1} = 1 12 3 4 30 6 7 48 9 selected_multiplied{2} = 8 24 8 2 12 4 1 42 9 selected_multiplied{3} = 1 48 3 9 48 1 2 18 3
  3 Comments
MarshallSc
MarshallSc on 16 Jul 2021
Thanks Walter!
On a different note, I don't know if it's allowed to say it here, but I just wanted to thank you Walter for all of your kind and invaluable helps with the codes. You personally hepled me out a lot so I wanted to show you my deepes gratitude; your kindness and the time you put into helping others don't go unnoticed man! Thank you!

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