Re: [R] editing a data.frame

From: john.polo <jpolo_at_mail.usf.edu>
Date: Mon, 09 Jun 2008 07:41:55 -0400

that did the trick. thanks a lot!

john

jim holtman wrote:
> Actually change the TreeTag to characters first because you are trying
> to store in a new factor value that is not there
>
> yr1bp$TreeTag <- as.character(yr1bp$TreeTag)
> yr1bp$TreeTag[1501]<-sub("1.00", "1", yr1bp$TreeTag[1501])
> # change back to a factor if desired
> yr1bp$TreeTag <- factor(yr1bp$TreeTag)
>
>
> On Sat, Jun 7, 2008 at 8:22 AM, jim holtman <jholtman_at_gmail.com
> <mailto:jholtman_at_gmail.com>> wrote:
>
> try:
>
> yr1bp$TreeTag[1501]<-sub("1.00", "1",
> as.character(yr1bp$TreeTag[1501]))
>
> Since it appears that TreeTag is a factor. This can be verified
> with 'str'.
>
>
> On Fri, Jun 6, 2008 at 11:22 PM, john.polo <jpolo_at_mail.usf.edu
> <mailto:jpolo_at_mail.usf.edu>> wrote:
>
> Daniel Folkinshteyn wrote:
>
> works for me:
> > sub('1.00', '1', '1.00E-20')
> [1] "1E-20"
>
> when i input what you wrote, i get the same result. but that
> doesn't change the value for TreeTag at row 1501, it's just
> floating around in space. if i try it for yr1bp$TreeTag[1501],
> which is 1.00E-20 i get this:
>
>
> > yr1bp$TreeTag[1501]<-sub("1.00", "1", yr1bp$TreeTag[1501])
> Warning message:
> In `[<-.factor`(`*tmp*`, 1501, value = "1E-20") :
> invalid factor level, NAs generated
>
> and then 1501 turns into:
> 1501 <NA> 2001 adult 32.5
>
> which is less useful than the way it was originally input.
> thanks for the suggestion.
>
> john
>
>
> finally, if all your target strings are of the form
> 1.00E-20, you could sub the whole thing with a more
> general regexp:
>
> sub("([0-9])(\.[0-9]{2})(.*)", "\\1\\3", yourvector)
> (it matches a digit, followed by a dot and two digits,
> followed by "anything else", and takes out the "dot and
> two digits" bit in the replacement, in the whole vector.)
>
> thanks for that suggestion. it could come in handy.
>
>
>
> on 06/06/2008 03:25 PM john.polo said the following:
>
> dear R users,
>
> the data frame (read in from a csv) looks like this:
> TreeTag Census Stage DBH
> 1 CW-W740 2001 juvenile 5.8
> 2 CW-W739 2001 juvenile 4.3
> 3 CW-W738 2001 juvenile 4.7
> 4 CW-W737 2001 juvenile 5.4
> 5 CW-W736 2001 juvenile 7.4
> 6 CW-W735 2001 juvenile 5.4
> ...
> 1501 1.00E-20 2001 adult 32.5
>
> i would like to change values under the TreeTag
> column. as the last value shows, some of the tags have
> decimals followed by 2 decimal places. i just want
> whole numbers, i.e. not 1.00E-20, but 1E-20. i have a
> rough understanding of regexp and grepped all the
> positions that have the inappropriate tags. i tried
> sub() a couple of different ways, like
> yr1bp$TreeTag[1501]<-sub("1.00", "1", yr1bp$TreeTag[1501])
> and after turning yr1bp$TreeTag[1501] into <NA>,
> yr1bp$TreeTag[1501]<-sub("", "1E-20", yr1pb$TreeTag[1501])
> and
> sub("", "1E-20", yr1bp$TreeTag[1501])
> but it's not working. i guess it has something to do
> with the data.frame characteristics i'm not aware of
> or don't understand. would i somehow have to tear
> apart the columns, edit them, and then put it back
> together? not that i know how to do that, but i'm
> wondering out loud.
>
> john
>



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