Re: [R] Help with Book example of Matrix application
On Apr 9, 2012, at 12:32 PM, James Lenihan wrote:
I found this example in an Introductory R book in the chapter on
Matrices and
Arrays
The array is
m
[,1] [,2] [,3] [,4] [,5]
[1,]0 12 138 20
[2,] 120 15 28 88
[3,] 13 15069
[4,]8 2860 33
[5,] 20 889 330
The code is
#returns the minimum value of d[i,j], i !=j and the row attaining
#the minimum, for square symmetric d; no special policy on ties
Would you consider a more compact operation? That code seems very unR-
ish.
min( m[row(m) != col(m)] )
#[1] 6
which(m == min( m[row(m) != col(m)] ), arr.ind=TRUE)
#
row col
[1,] 4 3
[2,] 3 4
---
c(min= min( m[row(m) != col(m)] ),
which(m == min( m[row(m) != col(m)] ), arr.ind=TRUE)[1,])
min row col
6 4 3
I suppose the question could be how to debug that code, in which case
you should be manually "stepping through" it to see what the values
are during the implicit loop.
mind <- function(d) {
n <- nrow(d)
# add a column to identify row number for apply()
dd <- cbind(d,1:n)
wmins <- apply(dd[-n,],1,imin)
# wins will be 2 X n, 1st row being indices and 2nd being values
i <- which.min(wmins[2,])
j <- wmins[1,i]
return(c(d[i,j],i,j))
}
#this finds the location, value of the minimum in a row x
imin <- function(x) {
lx <- length(x)
i <- x[lx] # original row number
j <-which.min(x[(x+1):(lx-1)])
k <- i+j
return(c(k,x[k]))
}
The result s/b
[1] 6 3 4
I am getting:
Warning messages:
1: In (x + 1):(lx - 1) :
numerical expression has 6 elements: only the first used
2: In (x + 1):(lx - 1) :
numerical expression has 6 elements: only the first used
3: In (x + 1):(lx - 1) :
numerical expression has 6 elements: only the first used
4: In (x + 1):(lx - 1) :
numerical expression has 6 elements: only the first used
I have check my typing a number of times.
Does anyone see an error?
Thanks,
Jim L.
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Re: [R] Help with Book example of Matrix application
On 09/04/2012 12:32 PM, James Lenihan wrote:
I found this example in an Introductory R book in the chapter on Matrices and
Arrays
You should probably check with the author of the book (there might be an
errata page posted somewhere), but it looks like a typo, in your code or
the original:
The array is
> m
[,1] [,2] [,3] [,4] [,5]
[1,]0 12 138 20
[2,] 120 15 28 88
[3,] 13 15069
[4,]8 2860 33
[5,] 20 889 330
The code is
#returns the minimum value of d[i,j], i !=j and the row attaining
#the minimum, for square symmetric d; no special policy on ties
mind<- function(d) {
n<- nrow(d)
# add a column to identify row number for apply()
dd<- cbind(d,1:n)
wmins<- apply(dd[-n,],1,imin)
# wins will be 2 X n, 1st row being indices and 2nd being values
i<- which.min(wmins[2,])
j<- wmins[1,i]
return(c(d[i,j],i,j))
}
#this finds the location, value of the minimum in a row x
imin<- function(x) {
lx<- length(x)
i<- x[lx] # original row number
j<-which.min(x[(x+1):(lx-1)])
That line doesn't make sense. Putting i in place of the innermost x
would make more sense, but wouldn't work in all cases: if i == lx,
you'll get a garbage answer.
Duncan Murdoch
k<- i+j
return(c(k,x[k]))
}
The result s/b
[1] 6 3 4
I am getting:
Warning messages:
1: In (x + 1):(lx - 1) :
numerical expression has 6 elements: only the first used
2: In (x + 1):(lx - 1) :
numerical expression has 6 elements: only the first used
3: In (x + 1):(lx - 1) :
numerical expression has 6 elements: only the first used
4: In (x + 1):(lx - 1) :
numerical expression has 6 elements: only the first used
I have check my typing a number of times.
Does anyone see an error?
Thanks,
Jim L.
[[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.
[R] Help with Book example of Matrix application
I found this example in an Introductory R book in the chapter on Matrices and
Arrays
The array is
> m
[,1] [,2] [,3] [,4] [,5]
[1,]0 12 138 20
[2,] 120 15 28 88
[3,] 13 15069
[4,]8 2860 33
[5,] 20 889 330
The code is
#returns the minimum value of d[i,j], i !=j and the row attaining
#the minimum, for square symmetric d; no special policy on ties
mind <- function(d) {
n <- nrow(d)
# add a column to identify row number for apply()
dd <- cbind(d,1:n)
wmins <- apply(dd[-n,],1,imin)
# wins will be 2 X n, 1st row being indices and 2nd being values
i <- which.min(wmins[2,])
j <- wmins[1,i]
return(c(d[i,j],i,j))
}
#this finds the location, value of the minimum in a row x
imin <- function(x) {
lx <- length(x)
i <- x[lx] # original row number
j <-which.min(x[(x+1):(lx-1)])
k <- i+j
return(c(k,x[k]))
}
The result s/b
[1] 6 3 4
I am getting:
Warning messages:
1: In (x + 1):(lx - 1) :
numerical expression has 6 elements: only the first used
2: In (x + 1):(lx - 1) :
numerical expression has 6 elements: only the first used
3: In (x + 1):(lx - 1) :
numerical expression has 6 elements: only the first used
4: In (x + 1):(lx - 1) :
numerical expression has 6 elements: only the first used
I have check my typing a number of times.
Does anyone see an error?
Thanks,
Jim L.
[[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.
