I have 30 .dat files named composite1.dat composite2.dat... etc. After importing them into matlab I need to ensure that the data is stored column-wise in a single matrix.(The name of the .DAT file refers to the column number it should be in matrix)

d = dir('composite*.dat');
nfiles = length(d);
X = [];
for k = 1:nfiles
 X = [X importdata(d(k).name)];
end