import complex column into matlab

Question

atib0539 2014-12-27

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回答： Matthew Parry 2019-11-7

Hi everybody,

I have a two-column data that I want to import into the workplace. The two columns are separated by comma, for all real numbers I could use the following code,

data = textread('data.txt', '', 'delimiter', ',');
x = data(1:(length(data(:,1))-1),1);     
y = data(1:(length(data(:,2))-1),2);

But now I have data after FFT like this, where the second column is complex,

0,-7.45678527326516E-7
0123532704572966,-9.13085574558244E-7 - 3.24050470823079E-7i
0247065409145915,-1.78617729703184E-6 + 9.66937131199859E-7i
0370598113718881,3.11409269891353E-6 - 1.40731487179325E-5i
0494130818291847,-8.23979324344331E-6 + 4.94108233557163E-5i
0617663522864795,3.95217467868805E-5 - 1.00035273201451E-4i
0741196227437761,-4.26665707593228E-5 + 7.19117803282971E-5i

How can I import it? The file can be saved as .txt, .csv, or .dat.

Thanks a lot!!

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dpb 2014-12-27

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Can you modify the process that writes the file any at all? If you would at least

a) Include the explicit zero imaginary part of the first row, and
b) eliminate the space between the sign and the numeric value for the imaginary component

it would be simpler to parse with standard formatting descriptors.

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Answer 1

per isakson 2014-12-27

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https://ww2.mathworks.cn/matlabcentral/answers/168226-import-complex-column-into-matlab#answer_163430

编辑：per isakson 2014-12-27

在 MATLAB Online 中打开

AFAIK: The complex number in the file need to be written without spaces between the real and the imaginary parts. However, I failed to find that stated in the documentation.

One way to read your file is to

read the entire file to one character string
remove the spaces
parse the string with the function, textscan

Try

    >> cac = cssm()
    cac = 
        [7x1 double]    [7x1 double]
    >> cac{1}
    ans =
             0
        0.0124
        0.0247
        0.0371
        0.0494
        0.0618
        0.0741
    >> cac{2}
    ans =
       1.0e-03 *
      -0.0007 + 0.0000i
      -0.0009 - 0.0003i
      -0.0018 + 0.0010i
       0.0031 - 0.0141i
      -0.0082 + 0.0494i
       0.0395 - 0.1000i
      -0.0427 + 0.0719i
    >>

where

    function    cac = cssm()
        str = fileread( 'cssm.txt' );
        str = strrep( str, ' ', '' );
        cac = textscan( str, '%f%f', 'Delimiter', ',' ); 
    end

and where cssm.txt contains

    0,-7.45678527326516E-7
0123532704572966,-9.13085574558244E-7 - 3.24050470823079E-7i
0247065409145915,-1.78617729703184E-6 + 9.66937131199859E-7i
0370598113718881,3.11409269891353E-6 - 1.40731487179325E-5i
0494130818291847,-8.23979324344331E-6 + 4.94108233557163E-5i
0617663522864795,3.95217467868805E-5 - 1.00035273201451E-4i
0741196227437761,-4.26665707593228E-5 + 7.19117803282971E-5i

&nbsp

Or use CollectOutput and read to one matrix

    >> cac = cssm()
    cac = 
        [7x2 double]
    >> cac{1}
    ans =
       0.0000 + 0.0000i  -0.0000 + 0.0000i
       0.0124 + 0.0000i  -0.0000 - 0.0000i
       0.0247 + 0.0000i  -0.0000 + 0.0000i
       0.0371 + 0.0000i   0.0000 - 0.0000i
       0.0494 + 0.0000i  -0.0000 + 0.0000i
       0.0618 + 0.0000i   0.0000 - 0.0001i
       0.0741 + 0.0000i  -0.0000 + 0.0001i

where

    function    cac = cssm()
        str = fileread( 'cssm.txt' );
        str = strrep( str, ' ', '' );
        cac = textscan( str, '%f%f', 'Delimiter',',', 'CollectOutput',true ); 
    end