[R] formatting POSIXlt object as strip labels in lattice plot

[John Field]

Dear list,

I'm plotting a lattice plot

xyplot(Volume ~ Weight | as.character(DateTime))

where DateTime is a POSIXlt object.  This produces strip labels in 
the format e.g. "2007-11-15 23:15:00" and panels are plotted in the 
correct order.  I'd prefer a format "15 Nov 23:15", but if I use 
format(DateTime,format="%d %b %H:%M") to do the conversion, then the 
panels are ordered according to the day of the month, ie the 
character string "15 Nov 23:15" etc.

How do I get labels in the required format, but panels in the correct order?

Thanks,
John

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