MATLAB: How to extract another matrix out of a big matrix

matrix extraction

Hello I have a big matrix including many rows and 2 columns. first column is the wavelengths. I need to extract another matrix out of it based on some specific wavelength value and I dont need the rest of data. for example this is my main matrix:
A=[420 0.23;421 0.26;422 0.25;423 0.24;424 0.28;425 0.27]
but I know that I just need values corresponding to (420 422 425) in the first column , so what i need is:
B=[420 0.23;422 0.25;425 0.27]
how can I ask to extract data for these three specific values in the first column? I cant refer to them by their position in matrix since it is not fix. thanks !

Best Answer

v = [420,422,425];
B = A(ismember(A(:,1),v),:);