reading complex data into a matlab array

Hi,

To keep it short: How can you read complex doubles into a matlab array from raw data files. To keep it long, see below.

I have a raw data file taken from an MR scanner. I have been using the IDL language to read/reconstruct it but my files have become large and the memory management in IDL is no longer good enough. I need to know how to read this data into matlab. The problem is in the data-type. IDL can create complex double arrays but it seems matlab cannot. The data is arranged as follows: header-->data-->header-->data... etc. I know how many bytes the headers are so i can move a pointer using fseek/fread etc however I do not know how to read in the data into an array. Each data point is a 16 byte complex number. If I dont move the pointers correctly then the data becomes scrambled etc. The data parts are structured: real --> IM --> real --> IM and so on. When I read in 16 bytes into IDL I get the correct values. It would be so simple if there were a complex double datatype in matlab. I've thought about parsing the data as I read it into a real and im matrix and then combining them afterwards but there must be an easier way?

Answer 1

[Jared]

If I understand the question correctly, something along these lines should work (although don't trust me on the fread syntax - it's been a while):

fp = fopen(file_of_interest);  
% code for reading the header, etc.

complex_matrix = complex(ones(final_size),ones(final_size));
for i=1:length(complex_matrix(:))
  complex_matrix(i) = complex(fread(fp,8,'*double'),fread(fp,8,'*double'));
end

% whatever other finalization you need to do
fclose(fp);

[Alex]

Thanks Jared,

Ill try this out!

[A]

What part of this solves the header->data->header->data?

I'm dealing with the same issue but not complex numbers. What exactly is the '8' in fread(fp,8,'*double") telling it to do? In that spot I currently have my matrix size [4x4]. Is there a way to not read in the header parts?

Answer 2

[Matthew Parry]

From R2019a onwards you can use the function readmatrix().