I have large files that are to be analysed, which are taken from a
recorder at 60 Hz. Sixty readings per second is far more than
necessary for my purposes, and I wondered whether there is a quick way
to 'refine' this data, like make a new file from the existing one that
has 5 or six readings per second.... What's the quickest way to do
this?

Any help would be appreciated!

Rob