How to compare the values of the same matrix?

I have a matrix 7x21 double. I need to compare each element of one column with each element of the remaining columns. By compare I mean if the elements are equal or almost equal (I have an uncertainty range in my data sheet). The output should tell me wich elements are equal

[Walter Roberson]

Duplicates https://www.mathworks.com/matlabcentral/answers/1460899-how-can-i-check-if-the-columns-of-my-matrix-have-value-in-common