[R] position of a string in a data frame
murdoch.duncan at gmail.com
Wed Apr 30 14:12:37 CEST 2014
On 30/04/2014, 8:02 AM, Frede Aakmann Tøgersen wrote:
> > foo <- data.frame(oid = 1:3, functions = c("mean", "sum", "sd"), type = c(TRUE, FALSE, TRUE))
> oid functions type
> 1 1 mean TRUE
> 2 2 sum FALSE
> 3 3 sd TRUE
>> foo == "sum"
> oid functions type
> [1,] FALSE FALSE FALSE
> [2,] FALSE TRUE FALSE
> [3,] FALSE FALSE FALSE
>> which(foo == "sum", arr.ind = TRUE)
> row col
> [1,] 2 2
> But can one risk this to fail if the class of some of the columns cannot be compared to a string?????
Yes, if some class declares that it's an error to compare it to a
string, this could fail.
> `==.foo` <- function(a, b) stop("don't do that")
> df <- data.frame(a=1)
> class(df$a) <- "foo"
> df == "abc"
Error in `==.foo`(left, right) : don't do that
The basic types allow comparison to strings.
> Yours sincerely / Med venlig hilsen
> Frede Aakmann Tøgersen
> Specialist, M.Sc., Ph.D.
> Plant Performance & Modeling
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>> -----Original Message-----
>> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
>> On Behalf Of carol white
>> Sent: 30. april 2014 13:42
>> To: r-help at stat.math.ethz.ch
>> Subject: [R] position of a string in a data frame
>> It might be a primitive question but how to find the position of a string in a
>> data frame? Suppose I search the word "sum" (case insensitive) in a data
>> frame and it is in the 7th row, 3rd column, how to retrieve the indices 7, 3? I
>> tried to use grep with tapply but it doesn't work.
>> Many thanks
>> [[alternative HTML version deleted]]
>> R-help at r-project.org mailing list
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> R-help at r-project.org mailing list
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> and provide commented, minimal, self-contained, reproducible code.
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