assigning numbers to string elements

Hi I have the following which creates 2 strings called left and right from a single string with the positions shifted by a single element.

pep='abcd';
sizepep=size(pep);
left=pep(1:(sizepep(2)-1));
right=pep(2:(sizepep(2)));
% so in this example left=abc and right = bcd
% if I were to assign numerical values to letters - eg.
a=1;
b=2;
c=3;
d=4;

How do I turn these two strings (left and right) into vectors so I can add each element together?

left=[1 2 3];
right=[2 3 4];
sum=[3 5 7]

Thank you in advance for advice.

[Walter Roberson]

Please avoid naming a variable "sum" as that interferes with using the MATLAB routine named "sum"

Answer 1

[Tushar Athawale]

It is possible to map strings to numeric arrays based on the predefined character maps. The following code snippet can be used in your example:

% Setup map
map('a')=1;
map('b')=2;
map('c')=3;
map('d')=4;

% Automatic setup invere of map (from map)
letter=map>0;
mapi(map(letter))=char(find(letter));

left = 'abc';
right = 'bcd';

% map string to numeric array.
left_code = map(left) 
right_code = map(right)

% You can also map numeric array to string 
left_decode = mapi(left_code)

sm = left_code + right_code;

Thanks to Bruno Luong for suggesting this approach in one of his posts in the MATLAB newsgroup:

https://www.mathworks.com/matlabcentral/newsreader/view_thread/236870

[KA]

Hi thank you for taking the time to answer this question sorry my reply took so long. Your answer works! but I have another question. Currently both left and right are taking values from the same map. Is it possible to adjust the script to have two unique maps. For example each letter has two different values depending if it is left or right?

Answer 2

[Walter Roberson]

 [~, left_code] = ismember(left, 'abcd');
 [~, right_code] = ismember(right, 'abcd');
 sum_code = left_code + right_code