[R] position of a string in a data frame

[Jim Lemon]

How about:

testdf<-data.frame(names=c("min","max","sum"),a=1:3,b=4:6,c=c(5,7,9))
which(tolower(as.matrix(testdf)) == "sum",arr.ind=TRUE)
      row col
[1,]   3   1

as.matrix coerces all elements to the lowest (character) mode, no?
Does it unclass anything like the example below?

Jim


On 04/30/2014 10:12 PM, Duncan Murdoch wrote:
> 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
>> M +45 2547 6050
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>> http://www.vestas.com
>>
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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
>>>
>>> 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
>>>
>>> [[alternative HTML version deleted]]
>>>
>>> ______________________________________________
>>> R-help at 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.
>>
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.