Hello,
What you need is to have your function return a list, not a vector. Like
this
testfun <- function (x, y) list(seq(x, y, 1))
testframe<-data.frame(xvalues=c(2,3),yvalues=c(4,5))
testframe$newcolumn <- apply(testframe, 1, function(x) testfun(x[1], x[2]))
class(testframe$newcolumn) # [1] "list"
Then you access lists and list elements.
testframe$newcolumn[[1]] # a list with just one element
testframe$newcolumn[[1]][[1]] # that element, a vector
testframe$newcolumn[[1]][[1]][2] # the vector's 2nd element
Since you want the function to return vectors in order to do further
computations, you'll access those vectors by varying the list index,
testframe$newcolumn[[1]][[1]] # first list, it's only vector
testframe$newcolumn[[2]][[1]] # second list, it's only vector
Etc.
Hope this helps,
Rui Barradas
Em 10-06-2012 12:29, Onur Uncu escreveu:
Thank you Duncan. A follow-up question is, how can I achieve the
desired result in the earlier email? (i.e. Add the resulting vectors
as a new column to the existing data.frame?) I tried the following:
testframe$newcolumn<-apply(testframe,1,function(x)testfun(x[1],x[2]))
but I am getting the following error:
Error in `$<-.data.frame`(`*tmp*`, "vecss", value = c(2, 3, 4, 3, 4, 5
: replacement has 3 rows, data has 2
Thanks for the help.
On Sun, Jun 10, 2012 at 12:02 PM, Duncan Murdoch
<murdoch.dun...@gmail.com> wrote:
On 12-06-10 6:41 AM, Onur Uncu wrote:
R-Help community,
I understand that data.frames can hold elements of type double, string
etc but NOT objects (such as a matrix etc).
That is incorrect. Dataframes can hold list vectors. For example:
A <- data.frame(x = 1:3)
A$y <- list(matrix(1, 2,2), matrix(2, 3,3), matrix(3,4,4))
A[1,2] will now extract the 2x2 matrix, A[2,2] will extract the 3x3, etc.
Duncan Murdoch
This is not convenient for
me in the following situation. I have a function that takes 2 inputs
and returns a vector:
testfun<- function (x,y) seq(x,y,1)
I have a data.frame defined as follows:
testframe<-data.frame(xvalues=c(2,3),yvalues=c(4,5))
I would like to apply testfun to every row of testframe and then
create a new column in the data.frame which holds the returned vectors
as objects. Why do I want this? Because the returned vectors are an
intermediate step towards further calculations. It would be great to
keep adding new columns to the data.frame with the intermediate
objects. But this is not possible since data.frames can not hold
objects as elements. What do you suggest as an elegant solution in
this scenario? Thank you for any help!
I would love to hear if forum
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