Here is a more R'sh solution (speed unknown). Courtesy of Mark Leeds (I
modified it a bit to generalize it for a cnt input and get min and max).
Again, getting cnt highest and lowest values in the entire matrix and
display the data point row and column names with each:
> x <- swiss$Education[1:25]
> dat = matrix(x,5,5)
> colnames(dat) = c('a','b','c','d','e')
> rownames(dat) = c('z','y','x','w','v')
> cnt = 10
> #===============================================
> print(dat)
a b c d e
z 12 7 6 2 10
y 9 7 12 8 3
x 5 8 7 28 12
w 7 7 12 20 6
v 15 13 5 9 1
>
> # MAKE IT A VECTOR FOR EASIER ORDERING
> datasvec <- as.vector(dat)
> # ORDER IT
> datasvecordered<- order(datasvec)
> # RECYCLE ROWS AND COLUMNS NAMES FOR EASIER MAPPING
> recycledcols <- rep(colnames(dat),each=nrow(dat))
> recycledrows <- rep(rownames(dat),times=ncol(dat))
>
> # GET THE VALUES, THE ROW NAMES AND THE COLUMN NAMES
> len = length(datasvecordered)
> rr_len = length(recycledrows)
>
rbind(datasvec[datasvecordered][(len-cnt):len],recycledrows[datasvecordered][(rr_len-cnt):rr_len],recycledcols[datasvecordered][(rr_len-cnt):rr_len])
[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10] [,11]
[1,] "9" "9" "10" "12" "12" "12" "12" "13" "15" "20" "28"
[2,] "y" "v" "z" "z" "y" "w" "x" "v" "v" "w" "x"
[3,] "a" "d" "e" "a" "c" "c" "e" "b" "a" "d" "d"
>
rbind(datasvec[datasvecordered][1:cnt],recycledrows[datasvecordered][1:cnt],recycledcols[datasvecordered][1:cnt])
[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
[1,] "1" "2" "3" "5" "5" "6" "6" "7" "7" "7"
[2,] "v" "z" "y" "x" "v" "z" "w" "w" "z" "y"
[3,] "e" "d" "e" "a" "c" "c" "e" "a" "b" "b"
enjoy
ben
On Wed, Oct 12, 2011 at 11:47 AM, Ben qant <ccqu...@gmail.com> wrote:
> Hello,
>
> This is my solution. This is pretty fast (tested with a larger data set)!
> If you have a more elegant way to do it (of similar speed), please reply.
> Thanks for the help!
>
> ################## get highest and lowest values and names of a matrix
> # create sample data
>
> x <- swiss$Education[1:25]
> dat = matrix(x,5,5)
> colnames(dat) = c('a','b','c','d','e')
>
> rownames(dat) = c('z','y','x','w','v')
>
> #my solution
>
> nms = dimnames(dat) #get matrix row and col names
> cnt = 10 # number of max and mins to get
>
> tmp = dat
> mxs = list("list",cnt)
> mns = list("list",cnt)
> for(i in 1:cnt){
> #get maxes
> mx_dims = arrayInd(which.max(tmp), dim(tmp)) # get max dims for entire
> matrix note: which.max also removes NA's
> mx_nm = c(nms[[1]][mx_dims[1]],nms[[2]][mx_dims[2]]) #get names
> mx = tmp[mx_dims] # get max value
> mxs[[i]] = c(mx,mx_nm) # add max and dim names to list of maxes
> tmp[mx_dims] = NA #removes last max so new one is found
>
> #get mins (basically same as above)
> mn_dims = arrayInd(which.min(tmp), dim(tmp))
> mn_nm = c(nms[[1]][mn_dims[1]],nms[[2]][mn_dims[2]])
> mn = tmp[mn_dims]
> mns[[i]] = c(mn,mn_nm)
> tmp[mn_dims] = NA
> }
>
> mxs
> mns
>
> # end
>
> Regards,
>
> Ben
>
>
> On Tue, Oct 11, 2011 at 5:32 PM, "Dénes TÓTH" <tde...@cogpsyphy.hu> wrote:
>
>>
>> which.max is even faster:
>>
>> dims <- c(1000,1000)
>> tt <- array(rnorm(prod(dims)),dims)
>> # which
>> system.time(
>> replicate(100, which(tt==max(tt), arr.ind=TRUE))
>> )
>> # which.max (& arrayInd)
>> system.time(
>> replicate(100, arrayInd(which.max(tt), dims))
>> )
>>
>> Best,
>> Denes
>>
>> > But it's simpler and probably faster to use R's built-in capabilities.
>> > ?which ## note the arr.ind argument!)
>> >
>> > As an example:
>> >
>> > test <- matrix(rnorm(24), nr = 4)
>> > which(test==max(test), arr.ind=TRUE)
>> > row col
>> > [1,] 2 6
>> >
>> > So this gives the row and column indices of the max, from which row and
>> > column names can easily be obtained from the dimnames attribute of the
>> > matrix.
>> >
>> > Note: This assumes that the object in question is a matrix, NOT a data
>> > frame, for which it would be slightly more complicated.
>> >
>> > -- Bert
>> >
>> >
>> > On Tue, Oct 11, 2011 at 3:06 PM, Carlos Ortega
>> > <c...@qualityexcellence.es>wrote:
>> >
>> >> Hi,
>> >>
>> >> With this code you can find row and col names for the largest value
>> >> applied
>> >> to your example:
>> >>
>> >> r.m.tmp<-apply(dat,1,max)
>> >> r.max<-names(r.m.tmp)[r.m.tmp==max(r.m.tmp)]
>> >>
>> >> c.m.tmp<-apply(dat,2,max)
>> >> c.max<-names(c.m.tmp)[c.m.tmp==max(c.m.tmp)]
>> >>
>> >> It's inmediate how to get the same for the smallest and build a
>> function
>> >> to
>> >> calculate everything and return a list.
>> >>
>> >>
>> >> Regards,
>> >> Carlos Ortega
>> >> www.qualityexcellence.es
>> >>
>> >> 2011/10/11 Ben qant <ccqu...@gmail.com>
>> >>
>> >> > Hello,
>> >> >
>> >> > I'm looking to get the values, row names and column names of the
>> >> largest
>> >> > and
>> >> > smallest values in a matrix.
>> >> >
>> >> > Example (except is does not include the names):
>> >> >
>> >> > > x <- swiss$Education[1:25]
>> >> > > dat = matrix(x,5,5)
>> >> > > colnames(dat) = c('a','b','c','d','c')
>> >> > > rownames(dat) = c('z','y','x','w','v')
>> >> > > dat
>> >> > a b c d c
>> >> > z 12 7 6 2 10
>> >> > y 9 7 12 8 3
>> >> > x 5 8 7 28 12
>> >> > w 7 7 12 20 6
>> >> > v 15 13 5 9 1
>> >> >
>> >> > > #top 10
>> >> > > sort(dat,partial=n-9:n)[(n-9):n]
>> >> > [1] 9 10 12 12 12 12 13 15 20 28
>> >> > > # bottom 10
>> >> > > sort(dat,partial=1:10)[1:10]
>> >> > [1] 1 2 3 5 5 6 6 7 7 7
>> >> >
>> >> > ...except I need the rownames and colnames to go along for the ride
>> >> with
>> >> > the
>> >> > values...because of this, I am guessing the return value will need to
>> >> be
>> >> a
>> >> > list since all of the values have different row and col names (which
>> >> is
>> >> > fine).
>> >> >
>> >> > Regards,
>> >> >
>> >> > Ben
>> >> >
>> >> > [[alternative HTML version deleted]]
>> >> >
>> >> > ______________________________________________
>> >> > R-help@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.
>> >> >
>> >>
>> >> [[alternative HTML version deleted]]
>> >>
>> >> ______________________________________________
>> >> R-help@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.
>> >>
>> >
>> > [[alternative HTML version deleted]]
>> >
>> > ______________________________________________
>> > R-help@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@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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