# I am looking for a way to include duplicates into ismember function

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Laurenz Boettger on 25 Apr 2022
Commented: Bruno Luong on 25 Apr 2022
Hi All,
I am looking for a solution to include duplicates into the ismember function. I have two tables, Table 1 with ages in one column, and an isotope value in the other column, and Table 2 just with ages. The ages in both tables differ, and I am looking for a way to find the closest fit of the ages in Table 1 for the ages in Table 2 to relate isotope values from Table 1 to ages in Table 2. For that, I have used:
b = interp1(a,a,y, 'nearest'); %where a=age Table 1 and y=age Table 2
To find the related isotope values I have used:
O = Osw(ismember(a,b)); %where Osw=isotope values from Table 1
This gives me all isotope values for the common ages in a and b, but just once, which gives me a shorter array than the length of the input tables since those have multiple values that are the same. Is there any way that the ismember function includes multiples/duplicates ,or does the operation for each row individually (I tried adding the "rows" command)? Every suggestion on how to solve this would be greatly appreciated. If anything should be unclear just ask, I'll try to explain it better. I hope someone who is more proficient with matlab can help me with this.
Cheers,
Laurenz

Bruno Luong on 25 Apr 2022
Edited: Bruno Luong on 25 Apr 2022
Why use ismember at all (at least in that way)?
O = Osw( interp1(a,1:length(a),y, 'nearest'))
##### 2 CommentsShowHide 1 older comment
Bruno Luong on 25 Apr 2022
If you insist on using ismember, reverse the arguments
b = interp1(a,a,y, 'nearest');
[~,ia] = ismember(b,a);
O = Osw(ia);

R2022a

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