Hybrid Matrix (strings, double elements)

I have a string-column-vector A and I have three set of data (three string-column-vectors B, C, D) associate to every element of A.

If I put these together to form a compact matrix (We call X), I cannot do operations between elements of B, C, D.

For example if I wanna do a difference between B and C, this is the error:

Undefined operator '-' for input arguments of type 'string'.

This is because my matrix is a string matrix. How can I make operations betweens the numeric values of matrix X?

A = ["wine"; "beer"; "water"; "The"];
B = [1  3  0.5  0.3];
C = [9  26  0.7  900];
D = [0  565  0  0.3];


% I create a compact matrix

X = [A B C D];


% Now I want to make a difference between B and C, but taking the element FROM MATRI X

diff = X(:,2) - X(:,3);

%But this is the error:
Undefined operator '-' for input arguments of type 'string'.

Answer 1

[Steven Lord]

Your concatenation operation (X = [A B C D];) converts the double arrays into string arrays. Instead what you probably want is a table array. I'm going to make one slight modification to your data (transposing B, C, and D.) I'm going to show you two different table arrays, one where A contains data and one where A contains "labels" for the rows of your data.

A = ["wine"; "beer"; "water"; "The"];
B = [1  3  0.5  0.3].';
C = [9  26  0.7  900].';
D = [0  565  0  0.3].';

T_data = table(A, B, C, D)
CminusB = T_data.C - T_data.B

T_label = table(B, C, D, 'RowNames', A)
CminusB2 = T_label.C - T_data.B

beerD = T_label("beer", "D")
waterAll = T_label{"water", :}

Answer 2

[madhan ravi]

 DifF = double(X(:,2)) - double(X(:,3)); % never name a variable diff!!