Do not use fgetl or fgets: on such a large file as this would be very slow. Use textscan, exactly as the MATLAB documentation recommends:
The third textscan input lets you specify a block size, which sets a limit to how many lines to read. So to read your required data into MATLAB without reading all of the data at once, you need to do the following in a loop (pseudocode, see link above):
out = {};
k = 0 ;
while ~feof(fileID)
k = k+1;
C = textscan(fileID,formatSpec,N);
out{end+1} = the columns you need
end
This reads each block, you extract and store the columns that you need, and then the rest of the data is discarded. In this way, all of the data is read into MATLAB, just not simultaneously! This is really quite fast :)
