3D array in MAT file ->DAT file to read in FORTRAN

BrandonPossible · 07-02-2009, 05:39 PM

Alright, so I have been trying to resolve this issue for awhile, but now feel like help is very necessary.

I have a 128(by)128(by)128 array in a MAT file, and am using the following MATLAB script to convert it to a DAT file:

load C_42.mat
fid=fopen('C_42.dat','wt')
fwrite(fid,Nu)
fclose(fid)

With it in the DAT format I am hoping to read it with a FORTRAN code, at which point I will be able to manipulate the array values and output it to a binary file.

Below is the read command in the FORTRAN code:

fn1='/home/C_42.dat'
open(11,file=fn1,form='FORMATTED')
read(11,'(4ES10.9)') u1,v1,w1
close(11)

Currently, I am getting a runtime error: Bad value during floating point read

(I am using gfortran)

I guess I am mainly lost on formatting, should I have used some sort of formatting in the MATLAB script in order to match the format in the FORTRAN code?

(When I open the MAT file in MATLAB it loads in the workspace as just a 3D matrix, Nu)

Thanks ahead for any possible help.

-B.P.

michaelk · 07-02-2009, 06:22 PM

Welcome to LinuxQuestions.

A DAT file is a generic term which really does not define a file format. Just because you write to a file called something.dat does not mean it will automatically be converted. I'm not a MatLab script person but what you posted is only coping the file and it is still in a mat format. You will have to use an export function i.e. to CSV for example and then your FORTRAN program will have to read and process the data accordingly.

colucix · 07-03-2009, 01:14 AM

Quote:

Originally Posted by BrandonPossible

With it in the DAT format I am hoping to read it with a FORTRAN code, at which point I will be able to manipulate the array values and output it to a binary file.

But fopen already write a binary file!!! If you want an ascii file you have to use fprintf. But you really don't need Fortran to manipulate data and re-write a file, if you can do that in Matlab.

Anyway, the only thing you have to pay attention is to create a binary file with access "direct" or "sequential". Your code creates the first one. In that case you have to specify access=direct in the open statement in Fortran. If you want to create a binary with sequential access, you have to add a signed 32-bit integer at the beginning and at the end of each record, containing the number of bytes to read. For example:

Code:

 >> nbytes = 128*128*128*4;
>> fid = fopen('C_42.dat','w');
>> fwrite(fid, nbytes, 'int32');
>> fwrite(fid, Nu, 'single');
>> fwrite(fid, nbytes, 'int32');
>> fclose(fid);

After that you can read the file in Fortran by this simple code:

Code:

program test
  real, dimension(128,128,128) :: Nu
  open(11, file = 'C_42.dat', form = 'unformatted')
  read(11) Nu
  close(11)
end program test