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$release.days==x,6] # as I have three
other
> columns that are not of interest
>
> vlookup(-12) = 1144, and so on, which is great.
>
> However, when I try:
>
> unlist(sapply(coll.minus.release,vlookup)) to apply it to the whole
> coll.minus.release
>
> it works up to a point, as it doesn't give me 132 values for the 132
values
> of coll.minus.release. Is this because the table of release.days and
> TotalParasitoid has less values than coll.minus.release (108 compared to
> 132)? To fill the gap I put in 0, and as none of the coll.minus.release
> values = 0 I think it wouldn't affect it.
I wager that a look at setdiff(coll.minus.release,release.days) and vice versa
would be illuminating. Notice that with your definition, vlookup(31415926) or
any other number absent from release.days gives a zero-length vector.
Presumably, you are looking for match().
>
> Other things I have tried include findInterval and match.
>
>
data[findInterval(x=data$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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>
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--
Peter Dalgaard
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Email: pd.mes at cbs.dk Priv: PDalgd at gmail.com