# How to find differences between 2 large tables that have a mix of string and numbers?

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Tanika Bawa on 17 Jul 2023
Commented: Peter Perkins on 18 Jul 2023
Hello! I have 2 very large tables that have the same number of rows and columns (20441x30), and I would like to know exactly which cells are different. I have tried 'Compare' in the Home tab, but it only tells me in the difference summary 'added', not which values/variables were added). I have also tried setdiff and ismember (error below), but it has a problem with one of my variables (maybe because it has NaNs too in the table).
Error using cell/union>cellunionR2012a (line 242)
Input A of class double and input B of class cell must be cell arrays of character vectors, unless one is a character
vector.
Do you know how I can compare tables that have a mix of string and numbers?
Thank you!
Dyuman Joshi on 17 Jul 2023
"(maybe because it has NaNs too in the table)"
FYI - MATLAB treats NaNs (as well as NaTs, <undefined> and <missing>) values as not equal to each other, nor equal to themselves as well.
If you want to compare NaNs (and others) and output true, use isequaln

Image Analyst on 17 Jul 2023
Have you tried iterating over every element of both tables using isequal to determine whether the locations are the same? Something like (untested)
[rows, columns] = size(table1);
matches = false(rows, columns); % Initialize to no matches (no equality).
for col = 1 : columns
for row = 1 : rows
% See if this location is equal.
% Set equality map to true if they're equal.
if isequal(table1{row, col}, table2{row, col})
matches(row, col) = true;
end
end
end
Alternatively you can compare the numeric columns using table2array and subtracting.
If you have any more questions, then attach your data and code to read it in with the paperclip icon after you read this:
Tanika Bawa on 17 Jul 2023
This worked well, thank you very much =)

Peter Perkins on 17 Jul 2023
Edited: Peter Perkins on 17 Jul 2023
I thnk looping over every row in the tables will not be very performant. I would think this will do better:
matches = false(size(table1));
for var = 1 : width(table1)
matches(:,var) = (table1.(var)==table2.(var)) ...
|| (ismissing(table1.(var)) && ismissing(table2.(var)))
end
That assumes the variables support ismissing; you might need a try/catch in general.
##### 3 CommentsShow 1 older commentHide 1 older comment
Tanika Bawa on 18 Jul 2023
thank you! =D
Peter Perkins on 18 Jul 2023
Yes, Voss is correct, & and |, not && and ||.

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