On Jun 3, 2011, at 12:43 PM, peter dalgaard wrote:
On Jun 3, 2011, at 16:59 , bjmjarrett wrote:
I am attempting to emulate the VLOOKUP function from Excel in R.
I want to compare one column (coll.minus.release) with another
(release.days) to get the number of parasitoid released at that time
(TotalParasitoids).
for example:
coll.minus.release release.days ParasitoidTotal
-12 -266 1700
8 -259 1000
8 -225 1000
28 -216 1000
41 -28 1148
77 -12 1144
105 0 1160
105 8 972
125 28 1146
125 41 1004
125 77 1003
125 97 1010
....
2772 NA NA
2801 NA NA
2834 NA NA
vlookup <- function(x) data[data$release.days==x,6] # as I have
three other
columns that are not of interest
vlookup(-12) = 1144, and so on, which is great.
However, when I try:
unlist(sapply(coll.minus.release,vlookup)) to apply it to the whole
coll.minus.release
it works up to a point, as it doesn't give me 132 values for the
132 values
of coll.minus.release. Is this because the table of release.days and
TotalParasitoid has less values than coll.minus.release (108
compared to
132)? To fill the gap I put in 0, and as none of the
coll.minus.release
values = 0 I think it wouldn't affect it.
I wager that a look at setdiff(coll.minus.release,release.days) and
vice versa would be illuminating. Notice that with your definition,
vlookup(31415926) or any other number absent from release.days gives
a zero-length vector.
Presumably, you are looking for match().
If I remember correctly VLOOKUP (and HLOOKUP) require sorted
cutpoints and picks the lowest number that the vector element exceeds
or equals. If so, then I suspect that an indexing strategy with
findInterval should work correctly if the dataframe is sorted with
order(). If you post a cut-pasteable example with desited input and
output, I sure someone can rig something up.
--
David.
Other things I have tried include findInterval and match.
data[findInterval(x=data$coll.minus.release,vec=data
$release.days,"ParasitoidTotal")]
didn't work as it said vec must be sorted non-decreasingly and
didn't work
when I randomised the release.days and ParasitoidTotal columns as
it doesn't
matter which order they are in.
Thanks for reading all the way through - I wanted all the
information I felt
you might need to help me in it.
Any help will be greatly appreciated.
--
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--
Peter Dalgaard
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Email: pd....@cbs.dk Priv: pda...@gmail.com
______________________________________________
R-help@r-project.org mailing list
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
David Winsemius, MD
West Hartford, CT
______________________________________________
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