Minor knit pick: errors

[<pl...@pi...>]

Hi,

it is not very helpful that gnuplot  does not distinguish between 
non-existent files and files it cannot parse for plotting.

  warning: Skipping unreadable file ......

Whenever I get this I have to try to work out whether there is a typo or 
come other error in the path specifier or whether there are some header 
lines or other formatting problems with data in a file  that it is able 
to find.


since these must be quite different error conditions as far as where and 
how they are trapped in the code, some distinction would be very helpful 
in saving time finding the problem.


Regards, Peter.