Hello again,
On Jan 17, 2010, at 5:42 PM, Rolf Turner wrote:
Notice that your output is 6 x 5 whereas your input is 5 x 6.
Now *what* did you do wrong?
Whoa! Let's try that again, but with a better example.
> X = matrix(as.character(1:6),2,3)
> X
[,1] [,2] [,3]
[1,] "1" "3" "5"
[2,] "2" "4" "6"
> apply(X,1,as.numeric)
[,1] [,2]
[1,] 1 2
[2,] 3 4
[3,] 5 6
Ouch! Hmmm. From the "Value" section of the apply docs... "If each
call to FUN returns a vector of length n, then apply returns an array
of dimension c(n, dim(X)[MARGIN]) if n > 1." Since I set MARGIN to 1,
then I was operating on rows where n is 3.
> c(n, dim(X)[MARGIN])
[1] 3 2
How about that; it does just what it says it will do. I have no idea
why it does that, but the remedy seems to be ...
> apply(X, c(1,2), as.numeric)
[,1] [,2] [,3]
[1,] 1 3 5
[2,] 2 4 6
... or even ...
> apply(X, 2, as.numeric)
[,1] [,2] [,3]
[1,] 1 3 5
[2,] 2 4 6
Perhaps someone could shed light on why the rows become columns.
Cheers,
Ben
cheers,
Rolf Turner
On 18/01/2010, at 11:33 AM, Ben Tupper wrote:
Hi,
I find the following works in R 2.10.1 on Mac OSX.
m = matrix(rep("3", 30), 5,6)
m
[,1] [,2] [,3] [,4] [,5] [,6]
[1,] "3" "3" "3" "3" "3" "3"
[2,] "3" "3" "3" "3" "3" "3"
[3,] "3" "3" "3" "3" "3" "3"
[4,] "3" "3" "3" "3" "3" "3"
[5,] "3" "3" "3" "3" "3" "3"
apply(m, 1,as.numeric)
[,1] [,2] [,3] [,4] [,5]
[1,] 3 3 3 3 3
[2,] 3 3 3 3 3
[3,] 3 3 3 3 3
[4,] 3 3 3 3 3
[5,] 3 3 3 3 3
[6,] 3 3 3 3 3
Cheers,
Ben
On Jan 17, 2010, at 5:17 PM, ivan popivanov wrote:
Hello,
This turned out to be surprisingly hard for me:
Let's say I have
mm = matrix(as.character(seq(1,30, 1)), nrow=3); mm
[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
[1,] "1" "4" "7" "10" "13" "16" "19" "22" "25" "28"
[2,] "2" "5" "8" "11" "14" "17" "20" "23" "26" "29"
[3,] "3" "6" "9" "12" "15" "18" "21" "24" "27" "30"
which is a matrix of strings, I'd like to convert this to a matrix
of the corresponding numbers:
nn = matrix(seq(1,30, 1), nrow=3), nn
[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
[1,] 1 4 7 10 13 16 19 22 25 28
[2,] 2 5 8 11 14 17 20 23 26 29
[3,] 3 6 9 12 15 18 21 24 27 30
I can convert each dimension using sapply(mm[,1], as.numeric), but
how to convert the full matrix?!
In fact I hit this problem because I got a data.frame consisting of
factors (numerics represented as strings) when I queried a database.
So if you can advise how to convert this data.frame to a data.frame
with proper numerics - that would be even better. The problem is
that my numerics are doubles and the data.matrix function seems to
cast factors to ints.
Thanks in advance,
Ivan
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Cheers,
Ben
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