[R] How to convert character matrix or data.frame to numeric?

[Rolf Turner]

In respect of your matrix problem:

(1) mode(mm) <- "numeric"

OR:

(2) mm <- apply(mm,2,as.numeric)

In respect of your data frame problem:

	as.data.frame(lapply(X,as.numeric))

(where X is your data frame) should work.  This will of course
convert every column of your data frame to numeric mode.  If there
are some columns that you wish to leave alone you will have to do
something a little bit more subtle.  But not much more subtle.
It's all pretty easy if you learn some basic R syntax.

	cheers,

		Rolf Turner

On 18/01/2010, at 11:17 AM, 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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