# Common substring index from two string arrays

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Preetham Manjunatha on 2 Nov 2021
Commented: Stephen on 2 Nov 2021
I have two string arrays a and b and I need to find the index matching the substring numbers (within string arrays). For example, in a string array a, 01, 02, 03 are the substrings matching in string array b.
a = {'frame01', 'frame02', 'frame03'};
a = string(a);
b = {'capture00.jpg' 'capture01.jpg', 'capture02.jpg', 'capture03.jpg', 'capture04.jpg'};
b = string(b)
Desired output index of string array b should be:
Index_b = [2 3 4]
Desired output index of string array a should be:
Index_a = [1 2 3]
Without for-loop solution is preferred.
Any help is appreciated!
Preetham Manjunatha on 2 Nov 2021
It is numbers with leading zeros in this example. But in general can be without leading zeros.

Stephen on 2 Nov 2021
a = ["frame01", "frame02", "frame03"];
b = ["capture00.jpg", "capture01.jpg", "capture02.jpg", "capture03.jpg", "capture04.jpg"];
[~,ia,ib] = intersect(regexp(a,'\d+','once','match'),regexp(b,'\d+','once','match'))
ia = 3×1
1 2 3
ib = 3×1
2 3 4
##### 2 CommentsShowHide 1 older comment
Stephen on 2 Nov 2021
And if you want to compare numeric values (i.e. disregard the leading zeros) then:
a = ["frame01", "frame02", "frame03"];
b = ["capture00.jpg", "capture01.jpg", "capture02.jpg", "capture03.jpg", "capture04.jpg"];
[~,ia,ib] = intersect(...
str2double(regexp(a,'\d+','once','match')),...
str2double(regexp(b,'\d+','once','match')))
ia = 3×1
1 2 3
ib = 3×1
2 3 4

R2021b

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