Skipping bytes in binary file

I have a binary file with the following values. The first 4 are each 2 bytes and double precision. The following are pairs of values of double precision. The bytes are unknown for the pair that follows. How can I use fread to skip the first 4 values (8 bytes) and extract the pairs?

1

2

3

4

1 2 4

2 2 5

4 4 4

[Jan]

"The first 4 are each 2 bytes and double precision." - Double precision means 8 bytes per value.

"The following are pairs of values of double precision." - Which pairs? I see triples.

[Tevin]

Oh sorry. The following are triples and I am trying to extract those.

Answer 1

[Voss]

You can just fread the appropriate number of bytes (i.e., the amount you want to skip). For example:

% read 4 double-precision numbers (32 bytes), and don't store the result
fread(fid,4,'double');

Or you can use fseek to move the file position indicator forward by the appropriate amount:

% move 32 bytes forward, effectively skipping those bytes
fseek(fid,32,'cof')

The next fread call reads from where fseek placed the file position indicator.

[Tevin]

Thank you. I am still not able to extract those triples.

[Walter Roberson]

triples = fread(fid, [3 NUMBER_OF_TRIPLES], 'uint8=>double') .';

Use inf for NUMBER_OF_TRIPLES if you want to read to end of file.

Each row of triples will be 3 entries, converted to double precision already -- ready for you to do calculations such as

triples(:,2) * 2^16 + triples(:,1) * 2^8 + triples(:,3)

or as appropriate depending what byte order is used for the triples.