Hybrid Matrix (strings, double elements)

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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'.

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Answer 1

Steven Lord 2020-7-17

编辑：Steven Lord 2020-7-17

在 MATLAB Online 中打开

1 个投票

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", :}