Import binary data to array

I have a file (sensor.lobe)(342848 bytes) containing binary data with the following data format:

Lokal ID    4 byte    signed int
data1       8 byte    double
data2       8 byte    double
data3       8 byte    double
data4       4 byte    unsigned int

little endian

How do I import, for example, data1 into an array?

I tried this:

 fid = fopen('sensor.lobe','r', 'l');
 status = fseek(fid,4,'bof'); 
 A = fread(fid, 8,'double', 'l');

The result does not make sense:

A =
  1.0e-314 *

    0.5300
    0.5305
    0.5308
    0.5310

Can anybody tell me what I am doing wrong?

Answer 1

[José-Luis]

status = fseek(fid,3,'bof');

Answer 2

[Image Analyst]

Here's an example of how I read a binary header with a variety of data types:

% Read_RAW_Header
% Returns the image header information and some extra information
% for our custom-defined raw image file.
% Usage: stHeader = Read_RAW_Header(filename)
% Input
%   filename - RAW format file name
% Output
%   stHeader - header structure containing information on the data
% Header is 44 bytes.
% The header of an RAW file will look something like this:
%  stHeader.TotalVoxels:  Array size - total size of the array (not the whole file) - number of voxels.
%  stHeader.NumberOfDimensions:  Number of dimensions - 3 for a 3D image.
%  stHeader.x_size:  Size (number of voxels) in the X direction.
%  stHeader.y_size:  Size (number of voxels) in the Y direction.
%  stHeader.z_size:  Size (number of voxels) in the Z direction.
%  stHeader.XStart:  Position of the center of the first pixel in the X direction - it's 0.
%  stHeader.YStart:  Position of the center of the first pixel in the Y direction - it's 0.
%  stHeader.ZStart:  Position of the center of the first pixel in the Z direction - it's 0.
%  stHeader.XEnd:  Position of the center of the last pixel in the X direction - it's voxelWidth * (sizeX - 1).
%  stHeader.Yend:  Position of the center of the last pixel in the Y direction - it's voxelWidth * (sizeY - 1).
%  stHeader.ZEnd:  Position of the center of the last pixel in the Z direction - it's voxelWidth * (sizeZ - 1).
% Following the header in the data file, are the voxel values, but of course we do not return these in the header.
%
% I also add these fields to the returned header argument:
%  stHeader.HeaderSize = 44;
%  stHeader.BytesPerVoxel
%  stHeader.FileSizeInBytes
%  stHeader.DataSizeInBytes
%  stHeader.Endian
%  stHeader.EndianArg
%
% Example usage:
% fullFileName_RAW = fullfile(cd, 'SimulatedData_Distance.RAW')
% stHeader = Read_RAW_Header(fullFileName_RAW)
%
%------------------------------------------------------------------------------

function stHeader = Read_RAW_Header(fullFilename)
  % Check syntax.  Must have at least one input argument, the full filename. 
  if (nargin ~= 1)
    error('Usage: stHeader = Read_RAW_Header(fullFilename)');
  end 

  if (ischar(fullFilename)~=1)
    error('Requires a string filename as an argument.');
  end 

  % These aren't in the header specification for this type of file,
  % but other formats use it and it's a useful thing to add to the header.
  stHeader.Endian = 'Big';
  stHeader.EndianArg = 'ieee-be';

  % Open the file for reading.
  fileHandleID = fopen(fullFilename, 'rb', stHeader.EndianArg);
  if (fileHandleID == -1)
    error(['Error opening ', fullFilename, ' for input.']);
  end

  % Go to the beginning of the file.
  % Shouldn't be necessary, but can't hurt.
  fseek(fileHandleID, 0, 'bof');

  % Read the total number of voxels in the image.
  % Read bytes 1-4.
  stHeader.TotalVoxels = fread(fileHandleID, 1, '*int32');
  % Note: this may be unreliable, and can be zero!
  % Better to take the x, y, and z sizes and multiply them together.

  % The next 4 bytes are the number of dimensions - 2 or 3.
  % Read bytes 5-8.
  stHeader.NumberOfDimensions = fread(fileHandleID, 1, 'int32');

  % Read in the dimensions for the different directions.
  % They'll be in bytes 9-20.
  stHeader.x_size = fread(fileHandleID, 1, '*int32');
  stHeader.y_size = fread(fileHandleID, 1, '*int32');
  stHeader.z_size = fread(fileHandleID, 1, '*int32');
  stHeader.TotalVoxels = stHeader.x_size * stHeader.y_size * stHeader.z_size;

  % Read in the position of the center of the first pixel.
  % They'll be in bytes 21-32.
  stHeader.XStart = fread(fileHandleID, 1, '*float');
  stHeader.YStart = fread(fileHandleID, 1, '*float');
  stHeader.ZStart = fread(fileHandleID, 1, '*float');
  % Read in the position of the center of the last pixel.
  % They'll be in bytes 33-44.
  stHeader.XFieldOfView = fread(fileHandleID, 1, '*float');
  stHeader.YFieldOfView = fread(fileHandleID, 1, '*float');
  stHeader.ZFieldOfView = fread(fileHandleID, 1, '*float');
  % Note: the fields of view are based on (pixel center) - to - (pixel center).

  % Calculate the voxel width.
  stHeader.VoxelWidth = stHeader.XFieldOfView / single(stHeader.x_size - 1);

  % Assign some other useful information.
  % It's not in the header but may come in useful anyway.

  % Assign the bytes per voxel.
  %fileInfo = imfinfo(fullFilename);  % Note: doesn't work!
  % fileSizeInBytes = fileInfo.FileSize;
  % This works:
  fileInfo = dir(fullFilename); 
  % MATLAB returns the information in a structure with fields:
  %    name
  %    date
  %    bytes
  %    isdir
  %    datenum
  stHeader.HeaderSize = 44;
  fileSizeInBytes = fileInfo.bytes;
  dataSizeInBytes = double(fileSizeInBytes) - double(stHeader.HeaderSize);
  stHeader.BytesPerVoxel = int32(round(dataSizeInBytes / double(stHeader.TotalVoxels)));
  stHeader.FileSizeInBytes = fileSizeInBytes;
  stHeader.DataSizeInBytes = dataSizeInBytes;

  % Close the file.
  fclose(fileHandleID);  % Close the file.

I see that I used '*float' and you used 'double' with no *.

Answer 3

[Jan]

You want to import 1 double only, not 8.

Alternatively you can read the data instead of skipping them:

fid     = fopen('sensor.lobe','r', 'l');
LokalID = fread(fid, 1, 'int32');
data1   = fread(fid, 1, 'double');
data2   = fread(fid, 1, 'double');
data3   = fread(fid, 1, 'double');
data4   = fread(fid, 1, 'uint32');

[Robert]

Your code gives me only one value per data type. I expect a serie of data for each data type(1,2,3 and 4). The data is the recording of pulses hitting a sensor over time, where the data are describing the characteristics of the pulses.

LokalID =

     0

data1 =

5.2998e-315

data2 =

5.3050e-315

data3 =

5.3076e-315

data4 =

   1.0748e+09