How do I turn string "C = A*B" to "data.C = data.A.*data.B " while the equation and variables may change?
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I'm building a GUI that reads simple formulas from an Excel file, then evaluate them as Matlab code. For example, the user may write "C=A*B" in an Excel cell, then Matlab will import the table and calculate a new variable C with the function eval. The problem is, the variables A and B are actually variables in a table, so the correct code should have been "data.C = data.A.*data.B ". The goal is to let the user create new variables without building a complicated calculator GUI.
The difficult part is, the names (A, B, C) are dynamic and there can be all sort of equations like "A=B+C/D" or "A=B^2-C". The name of the table itself is however fixed. How can I achieve that?
Voss on 27 Jun 2022
Edited: Voss on 27 Jun 2022
Maybe this is worth a try:
% example usage
% running it on a table
A = [1;2;3];
B = [4;5;6];
C = [7;8;9];
D = [10;11;12];
data = table(A,B,C,D)
function str = fix_formula(str)
str = regexprep(str,'\<([A-Za-z_]+)\>','data.$1'); % prepend variable names with "data."
str = regexprep(str,'([*/^\\])','.$1'); % replace operators *, /, ^, \ with .*, ./, .^, .\ (element-wise)