How to store vectors in a 3d matrix using a for loop

I imported the data from the file and I want to store the Ra and Nu values for each unique value of A in a 3d matrix using for loop.This is what I have so far:-

if true
  % code
end% Import data
Experimental_data = importdata('experimental_data_1.csv');
% Extract details
text_data=Experimental_data.textdata;
% Use for loop to restructure data
for i=1:length(A_unique);
  Ra=?
  Nu=?
  A_unique(:,:,i)=[Ra,Nu];
end
Pls guide me on how to write the for loop?
num_data = Experimental_data.data;
% Extract from columns
A=num_data(:,1);
Ra=num_data(:,2);
Nu=num_data(:,3);
% Find unique values of A
A_unique=unique(A);

[Adam]

You shouldn't need a loop. What does your data look like after you have imported it? Are A, Ra and Nu three separate variables?