# returning a unique array and comparing it with a different array.

3 views (last 30 days)
Tony Haines on 31 Jan 2024
Commented: Tony Haines on 13 Feb 2024
Hello,
I have a code that generates the y-coordinates of a few points, and returns the matrix as follows.
y_cosnode =
0.5833 0.6667 0.7500 0.8333 0.9167 1.0000
0.5000 0.5833 0.6667 0.7500 0.8333 0.9167
I wanted non-repeating values so I used y_cosnode = reshape(unique(y_cosnode),1,[]) . This gives me
y_cosnode =
0.5000 0.5833 0.6667 0.7500 0.8333 0.9167 1.0000
Now, I have another matrix array, a = [0.5000 0.5833 0.6667 0.7500 1] which I would like to compare each entry values with y_cosnode.
for i=1:size(y_cosnode,2)
[row,col] = find(y_cosnode(1,i)==a(1,:));
col
end
col =
1
col =
1x0 empty double row vector
col =
1x0 empty double row vector
col =
4
col =
1x0 empty double row vector
col =
1x0 empty double row vector
col =
5
obviously, 0.5833 and 0.6667 should not be empty because they are in matrix a. However, when I replace the matrix array 'y_cosnode', with
y_cosnode = [0.5000 0.5833 0.6667 0.7500 0.8333 0.9167 1.0000] which are the same values, just typed by myself, I get the following results. Which is what I'm looking for.
col =
1
col =
2
col =
3
col =
4
col =
1x0 empty double row vector
col =
1x0 empty double row vector
col =
5
Matt J on 1 Feb 2024
Edited: Matt J on 1 Feb 2024
0.5833 and 0.6667 should not be empty because they are in matrix a.
They are probably not in fact in matrix a. You're only displaying these numbers to 4 decimal places, so we cannot verify that the numbers agree beyond that.

Matt J on 1 Feb 2024
Edited: Matt J on 1 Feb 2024
The whole thing can be done in one line. No need for unique, reshape, or any of the rest of it.
result = ismembertol(a,y_cosnode(:),1e-6)
And if a nonlogical indices are really needed, you can add,
find(result)
Tony Haines on 13 Feb 2024
Thank you for your suggestion. All i needed was to add a tolerance value.

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