How can I apply a summary function to a time of day subset?
For example with:
r['T16:00/T17:00']$Value
How can I apply something like function (x) quantile(x, c(.90)) for Value over each day's sample hour?
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Kyle Brandt
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You can use apply.daily to apply a function to each day's data after you've done the time-of-day subset.
rt <- r['T16:00/T17:00','Value']
rd <- apply.daily(rt, function(x) xts(t(quantile(x,0.9)), end(x)))
You can see I needed to do a few backflips to ensure the object returned from your function can be handled by apply.daily. Mainly, it has to be a multi-column xts object with one row.
Joshua Ulrich
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`plot(apply.daily(rt, function(x) quantile(x, c(.90))))` Works ... is there a caveat with that? -- Oh I see, typo in my question so you were going off of that I think – Kyle Brandt Jan 31 '12 at 22:23
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@KyleBrandt: You're correct. I thought it was a bit odd, but I assumed you did it on purpose. :) I'll update my answer. – Joshua Ulrich Jan 31 '12 at 22:55