[R] Counting things in a time series.

Daniel Malter daniel at umd.edu
Sun Nov 21 12:48:16 CET 2010


Hi, these are pretty basic questions. You might want to pick up an
introductory manual.

Lets assume you have a time stamp that already indicates the hours. Assume
you have 300 observations, each of which falls in one of 24 hours of
observation. You easily get the number of obs in each hour with the table
command.

x=sample(1:24,300,replace=T)
table(x)

Let's now assume you don't have the observations binned yet. Then you can
'cut' the time stamp vector at intervals of your liking, and tabulate the
resulting occurrences of the factors. Assume as an example that you wanted
irregular intervals. You want to know how many occurrences there are between
midnight and 0900, 0900 and noon, noon and 1500, 1500 and 1800, and 1800 and
midnight.

nx=cut(x,c(0,9,12,15,18,24))
table(nx)

for the second question: ?as.ts()

HTH,
Daniel

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