# Comparing 2 columns of a matrix

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Gautami Golani on 23 Feb 2019
Commented: Star Strider on 24 Feb 2019
I want to compare 2 columns of my matrix as shown below:
For example, I have the number 4 in the first column occurring thrice. I need to compare it's corresponding values in column 2 and obtain the minimum value among them. I then need to store that value in another matrix.
Could someone suggest me a way to get this desired result.
Thanks and regards

Star Strider on 23 Feb 2019
Try this (using the accumarray (link) function):
A = [randi(10, 20, 1) rand(20,1)] % Create Data
[A1u,~,idx] = unique(A(:,1)); % Unique Values & Indices
MinVals = accumarray(idx, A(:,2), [], @(x)min(x)); % Find Minimum Of Each
Result = [A1u, MinVals] % Desired Result
Use your own matrix for ‘A’.
Star Strider on 24 Feb 2019
As always, my pleasure.

Image Analyst on 23 Feb 2019
You can do this easily with unique() and histogram() or histcounts(). Since you didn't include your data in a way that's easy for us to code up, I assume you'd prefer to do it yourself, so give it a try. If you run into problems, attach your data and explain the problem(s).
Gautami Golani on 23 Feb 2019
My code is as shown below. It's just a part of my entire program.
I'm trying to compare all the 3 values of the number 4.0000 in column 2 and find out the min of them.
Example: For 4.000 the corresponding values in column 2 are 0.0042, 0.0028 and 0.0015.
So my new matrix should have the min of these 3, which is 0.0015.
Thanks

R2018b

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