On 30/04/2014, 8:02 AM, Frede Aakmann Tøgersen wrote:
Try
> foo <- data.frame(oid = 1:3, functions = c("mean", "sum", "sd"), type =
c(TRUE, FALSE, TRUE))
foo
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.
For example,
> `==.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.
Duncan Murdoch
Yours sincerely / Med venlig hilsen
Frede Aakmann Tøgersen
Specialist, M.Sc., Ph.D.
Plant Performance & Modeling
Technology & Service Solutions
T +45 9730 5135
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-----Original Message-----
From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org]
On Behalf Of carol white
Sent: 30. april 2014 13:42
To: r-h...@stat.math.ethz.ch
Subject: [R] position of a string in a data frame
Hi,
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
Carol
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