[R] help using outer function
warthog29
gaylewind at gmail.com
Sun Aug 10 19:43:04 CEST 2008
Thanks Dan. You did much more than just answer my question.
Sincerely,
Dan Davison wrote:
>
> On Sun, Aug 10, 2008 at 06:00:21PM +0100, Dan Davison wrote:
>> On Sun, Aug 10, 2008 at 09:02:59AM -0700, warthog29 wrote:
>> >
>> > Hi,
>> > I would like to use the R's outer function on y below so that I can
>> subtract
>> > elements from each other. The resulting dataframe is symmetric, save
>> for the
>> ^^^^^^
>> outer() returns a matrix, not a data frame.
>>
>> > negative signs on the other half of the numbers. I would like to get
>> only
>> > half of the dataframe. Here is the code I wrote (it is returning only
>> the
>> > first line of the all elements I want. Please help).
>> > y<-c(4,4,3.9,3.8,3.7,3.6,3.5,3.5,3.5,3.3,3.2,3.2)
>> >
>> > b<-outer(y,y,"-")
>>
>> > b<-as.matrix(by)
>>
>> I assume that line was supposed to be b<-as.matrix(by). In any case
>
> Hmm, I didn't really clarify things there. I meant
> b<-as.matrix(b). But anyway, not needed.
>
>> you don't need it; b is a matrix already.
>>
>> > # I want to keep the elements:
>> > #b[1,2:12],
>> > #b[2,3:12],
>> > #.........until
>> > #b[11,12:12].
>>
>> Use upper.tri() to get the upper-triangle:
>>
>> b[upper.tri(b, diag=FALSE)]
>> [1] 0.0 0.1 0.1 0.2 0.2 0.1 0.3 0.3 0.2 0.1 0.4 0.4 0.3 0.2 0.1 0.5 0.5
>> 0.4 0.3
>> [20] 0.2 0.1 0.5 0.5 0.4 0.3 0.2 0.1 0.0 0.5 0.5 0.4 0.3 0.2 0.1 0.0 0.0
>> 0.7 0.7
>> [39] 0.6 0.5 0.4 0.3 0.2 0.2 0.2 0.8 0.8 0.7 0.6 0.5 0.4 0.3 0.3 0.3 0.1
>> 0.8 0.8
>> [58] 0.7 0.6 0.5 0.4 0.3 0.3 0.3 0.1 0.0
>>
>> Or perhaps you want to knock out the negative entries, but still keep the
>> matrix structure:
>>
>> b[lower.tri(b)] <- NA
>>
>> or perhaps you wanted
>>
>> b <- abs(outer(y,y,"-"))
>>
>> in the first place?
>>
>> > #Here is the function I wrote to get half of matrix:
>> >
>> > wk<-function(p){
>> > for (i in 2:p){
>> > ri<-b[i-1,i:p]
>> > return(ri)
>> > }
>> > }
>> > wk(12)
>> > #[1] 0.0 0.1 0.2 0.3 0.4 0.5 0.5 0.5 0.7 0.8 0.8
>>
>> I think you were intending this function to be something like this
>>
>> wk<-function(p){
>> ri <- NULL
>> for (i in 2:p){
>> ri<-c(ri, b[i-1,i:p])
>> }
>> return(ri)
>> }
>>
>> Note that this function will give a different result from upper.tri(),
>> because you are concatenating elements in the *rows* of the matrix,
>> whereas the way matrices are represented in R has consecutive elements
>> running down the columns. I.e. look at
>>
>> > A <- matrix(nrow=2,ncol=2)
>> > A
>> [,1] [,2]
>> [1,] NA NA
>> [2,] NA NA
>> > A[] <- 1:4
>> > A
>> [,1] [,2]
>> [1,] 1 3
>> [2,] 2 4
>>
>> Dan
>>
>> >
>> > As you can see, it is only returning the first line. I would like other
>> > corresponding elements too, to be found in row 2 to 12. Thanks.
>> > --
>> > View this message in context:
>> http://www.nabble.com/help-using-outer-function-tp18914432p18914432.html
>> > Sent from the R help mailing list archive at Nabble.com.
>> >
>> > ______________________________________________
>> > 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.
>
>
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