using function to remove elements from a large matrix

I need to code for a matrix in which the rows are removed given thier value in a certain column is not of desire to me. eg, I want to keep the numbers 1 2 3 and 11 and 12 but not 4 5 6 or 13 14 etc.

[Malik Khan]

It does not have to be a function.

[KALYAN ACHARJYA]

Have you tried, please show your efforts?

[Malik Khan]

I have not attempted this yet because I have no idea where to start

Answer 1

[the cyclist]

idxToKeep = ismember(M(:,2),[1,2,3,11,12]);
M = M(idxToKeep,:);