Removing row with smallest value, for a given factor
On 2011-04-23 07:02, David Winsemius wrote:
On Apr 23, 2011, at 9:05 AM, - - wrote:
I have a table.
First column is a date, second column is an index and other columns
contains some other values.
I want to remove, for each date, the row with the smallest index (it
is not necessarily 1).
ex: in the following table, I want to remove row 1 (2013-05-12 with
index 2) and row 8 (2013-05-13 with index 1)
day index values
1 2013-05-12 2 xxxx
2 2013-05-12 3 xxxx
3 2013-05-12 4 xxxx
4 2013-05-12 5 xxxx
5 2013-05-12 6 xxxx
6 2013-05-12 7 xxxx
7 2013-05-12 8 xxxx
8 2013-05-13 1 xxxx
9 2013-05-13 3 xxxx
10 2013-05-13 4 xxxx
11 2013-05-13 5 xxxx
12 2013-05-13 6 xxxx
13 2013-05-13 7 xxxx
14 2013-05-13 8 xxxx
15 2013-05-13 9 xxxx
16 2013-05-13 10 xxxx
17 2013-05-13 12 xxxx
Consider using ave and creating a logical vector that you then negate:
> ave(dat$index, list(dat$day), FUN=function(x) x==min(x))
[1] 1 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 dat[ -ave(dat$index, list(dat$day), FUN=function(x) x==min(x)), ]
ave() is one of those really handy functions, but I think that you meant dat[ !ave(dat$index, list(dat$day), FUN=function(x) x==min(x)), ] Here's another way, using the plyr package require(plyr) ddply(dat, .(day), .fun = function(x) subset(x, index != min(index))) Peter Ehlers
-- David Winsemius, MD West Hartford, CT
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