[R] No "number of days" format for 'difftime'?
loris.bennett at fu-berlin.de
Mon Aug 8 16:43:10 CEST 2016
Martin Maechler <maechler at stat.math.ethz.ch> writes:
>>>>>> Loris Bennett <loris.bennett at fu-berlin.de>
>>>>>> on Mon, 8 Aug 2016 14:12:47 +0200 writes:
> > Loris Bennett <loris.bennett at fu-berlin.de> writes:
> >> Thanks for the link, John. However, there is a hyphen missing. It
> >> should be:
> >> http://www.dummies.com/how-to/content/how-to-read-errors-and-warnings-in-r.html
> >> Appropriately, with the correct URL we find the too often forgotten
> >> pearl of wisdom:
> >> "Chances are, you just typed something wrong there."
> >> I think I need this on my coffee cup.
> >> Cheers,
> >> Loris
> > Continuing the topic for my future self and others equally poorly versed
> > in The Art and Dark Science of Interpreting R Error Messages, if I have
> > the following in the file "my_data"
> > 1094165 2016-07-24T09:40:02 13-23:03:28 1 COMPLETED
> > 1112076 2016-08-01T14:45:49 6-13:26:15 1 COMPLETED
> > and do
> >> d <- read.table("my_data")
> >> colnames(d) <- c("jobid","start","elapsed","alloccpus","state")
> >> df <- transform(d,start = as.POSIXct(start,format="%Y-%m-%dT%H:%M:%S"),elapsed = as.difftime(elapsed,format="%d-%H:%M:%S"))
> > I get the following:
> > Error in as.difftime(elapsed, format = "%d-%H:%M:%S") :
> > 'tim' is not character or numeric
> Well, let me argue that you should have found this to be a *helpful*
> error message. You are no complete beginner anymore, right,
> 1) the error is in your use of as.difftime().
> 2) ?as.difftime or str(difftime)
> both clearly indicate that 'tim' is the first argument of as.difftime,
> and I really do wonder why you continued with the infamous
> "trial-and-error programming technique" instead of reading or at
> least quickly browsing the relevant reference, i.e., help page
My apologies, you are absolutely right - I see the error of my ways.
The only feeble defence I can mount is that the usage example from
as.difftime(tim, format = "%X", units = "auto")
superficially disguises the fact that the first argument is also a named
argument with the name 'tim'. I think I had assumed that the initial
argument were always positional, e.g. as for paste0
paste0(..., collapse = NULL)
However, I now realise that '...' also generates named arguments, e.g.
So as a non-beginner but infrequent R user, in future I shall try use
the explicit form more often, e.g.
as.difftime(tim = "4-03:02:01", format = "%d-%H:%M:%S")
to remind myself what I am doing.
So fortune(350) really is true. I just didn't believe enough to read
Dr. Loris Bennett (Mr.)
ZEDAT, Freie Universität Berlin Email loris.bennett at fu-berlin.de
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