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how to read complex file data to matrix

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saihua lin
saihua lin on 17 Jan 2020
Edited: per isakson on 18 Jan 2020
I have a.txt file, with complex data. the format is
1.958138021e-02 0.64646110658609712285 + 0.093290941560866688653j
1.958139648e-02 0.32117256288141476928 - 0.061542254916540022058j
1.958141276e-02 -0.22359569118086644601 + 0.3585713533321416846j
1.958142904e-02 -0.22397218216792619261 + 0.082213621398327246803j
1.999960938e-02 0
1.999962565e-02 0
1.999964193e-02 0
1.999965820e-02 0
2.000000000e-02 0.10412797744247889731 + 0.0081123700776114041067j
There's space between + and -. how can I read this file into a matrix with seperated I part and Q part.
like
1.958138021e-02 0.64646110658609712285 0.093290941560866688653
...
1.999960938e-02 0 0
2.000000000e-02 0.10412797744247889731 0.0081123700776114041067

  2 Comments

stozaki
stozaki on 17 Jan 2020
Could you attach a real text file?

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Accepted Answer

per isakson
per isakson on 17 Jan 2020
Following Walter's advise
%%
chr = fileread('a.txt');
%%
chr = strrep( chr, ' + ', '+' );
chr = strrep( chr, ' - ', '-' );
cac = textscan( chr, '%f%f' );
%%
M = cat( 2, cac{1}, real(cac{2}), imag(cac{2}) );
>> M(1:3,:)
ans =
0 0.10413 0.0081124
1.6276e-08 -0.04608 -0.073765
3.2552e-08 -0.038321 0.076231

  1 Comment

saihua lin
saihua lin on 17 Jan 2020
thank you. This works and is fast. I find there's another code by reading line by line. It works but is very slow. Your method is faster
fid = fopen ('a.txt','r');
ii = 1;
while ~feof(fid)
acorrente(ii, :) = str2num(fgets(fid));
ii = ii + 1;
end
fclose(fid);
data = [real(acorrente(:,1)) real(acorrente(:,2)) imag(acorrente(:,2))];

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More Answers (1)

Walter Roberson
Walter Roberson on 17 Jan 2020
Sometimes easiest is to read the file as a character vector, use regexp to remove the space around the sign of the imaginary part, and then textscan. textscan and other numeric formats can read complex values when there is no space.
Or read the file as string and regexp to change lines that do not end in j to append + 0j on them. With all lines having the same format you can easily textscan to extract real and imaginary separately.

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