MATLAB: Issue with saving real and imag values to a text file

fprintfMATLAB

I have two sets of data to be mapped onto a grid to their respective indices as shown in my below code. However, when I try to save the data to a text file, it is not considering the sign(+/-) of the imaginary value into account.
clc;
grid = zeros(4,2,1);
index_1 = (1:4)';
index_2 = (5:7)';
Data_1 = [1+1i,2-2i,-3+3i,-4-4i]';
Data_2 = [101+101i,202+202i,303+303i]';
grid(index_1) = Data_1;
grid(index_2) = Data_2;
fileID = fopen('SaveData.txt','w');
fprintf(fileID,'%i,%i\n',[grid(:),grid(:)]');
fclose(fileID);
Incorrect sign(+/-) is saved as shown below. If the real value is negative, it automatically considers the imaginary value also as negative. Could someone help me fix this.
1,1
2,2         % Expected : 2,-2
-3,-3       % Expected : -3,3
-4,-4   
101,101
202,202
303,303
0,0

Best Answer

You need to explicitly obtain the real and imaginary parts, before printing with fprintf:
M = [real(grid(:)),imag(grid(:))];
and then simply use this in fprintf:
fileID = fopen('SaveData.txt','w');
fprintf(fileID,'%i,%i\n',M.');
fclose(fileID);
The fprintf documentation states that "Numeric conversions print only the real component of complex numbers". So "Incorrect sign(+/-) is saved...": is not true: actually the negative sign is totally correct, for the real part of the number, which is exactly what you printed in your file.
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