How do I read a file with complex data (real + imaginary) into a vector?

>> C = dlmread( 'data.txt' )
C =
  Columns 1 through 3
        1.868 -    0.52591i      -0.4178 +     1.0316i       0.5408 -    0.74036i
      0.33257 -    0.20658i     -0.56193 -     1.6297i      -0.3833 +      0.555i
       0.6894 +    0.60439i       1.2882 +    0.12116i       1.0911 +    0.40315i
      0.36288 +     1.0868i      -0.7524 +    0.72005i      -1.8897 +    0.25002i
  Columns 4 through 6
    -0.024144 +     1.6425i     -0.34343 +    0.96012i            0 +          0i
      0.58934 -   0.053148i      0.18756 -    0.53192i      -1.0676 +    0.88013i
     -0.63711 -    0.91396i     -0.70589 +    0.54294i     -0.28131 +    0.41173i
       1.3212 +     1.9887i            0 +          0i            0 +          0i
>> 

where data.txt contains the data of your comment,

"a vector of 70: [] ?"

D = reshape( C, 6,[] ); % I replaced 70 by 6 to match this small data set

"If row 1 is bigger than row 2, then I like the row 1 padded"

You don't mean to pad the "bigger" row?

In response to comments

This script does for the large file what dlmread() did for the small file

%%
fid = fopen( 'd:\m\cssm\BerNoisySignal.dat', 'rt' );
cac = cell(0,1);
while not( feof( fid ) )
    chr = fgetl( fid );
    cac{end+1,1} = textscan( chr, '%f', 'Delimiter','\t' );
    disp( length(cac) )    % show progress
end
fclose( fid );
%%
wid = max( cellfun( @(c) numel(c{1}), cac ) );
C = complex( zeros( length(cac), wid ) );
%%
for jj = 1 : length(cac)
   num = reshape( cac{jj}{1}, 1,[] ); 
   C(jj,1:length(num)) = num;
end
%%
figure,imagesc(real(C))

outputs

and

>> C(30:35,1e5:1e5+2)
ans =
        0.473 +    0.24055i     -0.10531 +    0.21882i      0.60661 +    0.44345i
      0.30427 +    0.43949i      0.75655 -     1.0476i      0.20642 +    0.40645i
      0.82177 -    0.10199i      0.17799 +    0.10666i      0.44184 +    0.88519i
      0.29776 -    0.44033i     -0.25417 +  0.0089458i    -0.048546 +     0.9869i
      0.96475 +    0.48504i     -0.58236 -     0.7256i    -0.019985 -     0.6513i
       1.1374 -     0.1369i      0.19644 -   0.021786i      -1.0417 -    0.55171
>> C(28:33,wid-2:wid)
ans =
            0 +          0i            0 +          0i            0 +          0i
            0 +          0i            0 +          0i            0 +          0i
     -0.22192 +    0.68818i     -0.91552 -    0.17804i      -0.2485 +    0.90526i
            0 +          0i            0 +          0i            0 +          0i
            0 +          0i            0 +          0i            0 +          0i
            0 +          0i            0 +          0i            0 +          0i       

and

>> D = reshape( C, 70,[] );
>> whos C D
  Name       Size                   Bytes  Class     Attributes
  C         35x155000            86800000  double    complex   
  D         70x77500             86800000  double    complex  