On Sep 6, 2010, at 12:15 PM, Dimitri Shvorob wrote:
I have a (very big - 1.5 rows) dataframe with a (POSIXt" "POSIXlt")
column h
(hour). Surprisingly, I cannot calculate a simple aggregate over the
dataframe.
n.h1 = sqldf("select distinct h, count(*) from x group by h")
Error in sqliteExecStatement(con, statement, bind.data) :
RS-DBI driver: (error in statement: no such table: x)
In addition: Warning message:
In value[[3L]](cond) : RAW() can only be applied to a 'raw', not a
'double'
n.h2 = aggregate(x$price, by = x$h, FUN = nrow)
A vector argument (x$price) would only have one row (at most).
nrow(c(1,2)
NULL
Error in names(y) <- c(names(by), names(x)) :
'names' attribute [10] must be the same length as the vector [2]
Try:
tapply(x$price, by = x$h, FUN = length)
--
David.
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