Hi everybody, could anyone help me in finding a way for selecting from a dataframe each row that comes before another that matches a condition? EXAMPLE: df raw.number name date temp 1 aaa 2001-04-15 15 2 aaa 2001-01-15 12 3 aaa 2001-03-15 13 ... i-1 bbb 2002-04-15 15 i bbb 2002-03-15 14 the condition is: df$temp==15 matching raws are 1 and i-1: I need something to select (only) rows where date=one month before the matching raws, so raws 3 and i. (the variable name has more than one level) Thanks
select previous date
2 messages · alessandro carletti, Ben Rich
You can try this:
dates <- df$date[df$temp==15]
one.month.before <- sapply(strsplit(dates, "-"), function(x)
paste(x[1], sprintf("%02d", as.numeric(x[2])-1), x[3], sep="-"))
df[df$date %in% one.month.before,]
Ben
On 8/18/05, alessandro carletti <alxmilton at yahoo.it> wrote:
Hi everybody, could anyone help me in finding a way for selecting from a dataframe each row that comes before another that matches a condition? EXAMPLE: df raw.number name date temp 1 aaa 2001-04-15 15 2 aaa 2001-01-15 12 3 aaa 2001-03-15 13 ... i-1 bbb 2002-04-15 15 i bbb 2002-03-15 14 the condition is: df$temp==15 matching raws are 1 and i-1: I need something to select (only) rows where date=one month before the matching raws, so raws 3 and i. (the variable name has more than one level) Thanks
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