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Juergen Rose

2009-Apr-16 14:14 UTC

[R] Howto build combinations of colums of a data frame

Hi,

as a R-newcomer I would like to create some new data frames from a given
data frame. The first new data frame should content all pairs of the
columns of the original data frame. The second new data frame should
content all tripels of of the columns of the original data frame and the
last the quadrupel of columns. The values in the new data frames should
be the product of two, three our four original single field values. For
pairs and tripels I could realize that task, with the following R
script:

Lines <- "a    b    c    d
    13     0    15   16
    23    24    25    0   
    33    34     0   36
     0    44    45   46
    53    54     0   55"

DF <- read.table(textConnection(Lines), header = TRUE)

nrow <-length(rownames(DF))
cnames <- colnames(DF)
nc <-length(DF)

nc.pairs <- nc*(nc-1)/2
#  initialize vector
cnames.new <- c(rep("",nc.pairs))
ind <- 1
print(sprintf("nc=%d",nc))
for (i in 1:(nc-1)) {
  if (i+1 <= nc ) {
    for (j in (i+1):nc) {
      cnames.new[ind] <- paste(cnames[i],cnames[j],sep="")
      ind <- ind+1
    }
  }
}

ind <- 1
#  initialize data.frame
pairs <- data.frame(matrix(c(rep(0,nc.pairs*nrow)),ncol=nc.pairs))
for (i in 1:nc) {
  if (i+1 <= nc ) {
    for (j in (i+1):nc) {
      t <- DF[,i] * DF[,j]
      pairs[[ind]] <- t
      ind <- ind+1
    }
  }
}
colnames(pairs) <- cnames.new
print("pairs=");   print(pairs)

nc.tripels <- nc*(nc-1)*(nc-2)/6
#  initialize vector
cnames.new <- c(rep("",nc.tripels))
ind <- 1
print(sprintf("nc=%d",nc))
for (i in 1:nc) {
  if (i+1 <= nc ) {
    for (j in (i+1):nc) {
      if (j+1 <= nc ) {
        for (k in (j+1):nc) {
          cnames.new[ind] <-
paste(cnames[i],cnames[j],cnames[k],sep="")
          ind <- ind+1
        }
      }
    }
  }
}

ind <- 1
#  initialize data.frame
tripels <- data.frame(matrix(c(rep(0,nc.tripels*nrow)),ncol=nc.tripels))
for (i in 1:(nc-1)) {
  if (i+1 <= nc ) {
    for (j in (i+1):nc) {
      if (j+1 <= nc ) {
        for (k in (j+1):nc) {
          t <- DF[,i] * DF[,j] * DF[,k]
          tripels[[ind]] <- t
          ind <- ind+1
        }
      }
    }
  }
}
colnames(tripels) <-  cnames.new
print("tripels=");   print(tripels)

I suppose that here is a much shorter way to get the same results. Any
hint is very much appreciated.

Regards

David Winsemius

2009-Apr-16 14:59 UTC

head link

[R] Howto build combinations of colums of a data frame

On Apr 16, 2009, at 10:14 AM, Juergen Rose wrote:
> Hi,
>
> as a R-newcomer I would like to create some new data frames from a  
> given
> data frame. The first new data frame should content all pairs of the
> columns of the original data frame. The second new data frame should
> content all tripels of of the columns of the original data frame and  
> the
> last the quadrupel of columns. The values in the new data frames  
> should
> be the product of two, three our four original single field values.  
> For
> pairs and tripels I could realize that task, with the following R
> script:
>
> Lines <- "a    b    c    d
>    13     0    15   16
>    23    24    25    0
>    33    34     0   36
>     0    44    45   46
>    53    54     0   55"
>
> DF <- read.table(textConnection(Lines), header = TRUE)
>
> nrow <-length(rownames(DF))
> cnames <- colnames(DF)
> nc <-length(DF)
>
> nc.pairs <- nc*(nc-1)/2
> #  initialize vector
> cnames.new <- c(rep("",nc.pairs))
> ind <- 1
> print(sprintf("nc=%d",nc))
> for (i in 1:(nc-1)) {
>  if (i+1 <= nc ) {
>    for (j in (i+1):nc) {
>      cnames.new[ind] <- paste(cnames[i],cnames[j],sep="")
>      ind <- ind+1
>    }
>  }
> }
>
> ind <- 1
> #  initialize data.frame
> pairs <- data.frame(matrix(c(rep(0,nc.pairs*nrow)),ncol=nc.pairs))
> for (i in 1:nc) {
>  if (i+1 <= nc ) {
>    for (j in (i+1):nc) {
>      t <- DF[,i] * DF[,j]
>      pairs[[ind]] <- t
>      ind <- ind+1
>    }
>  }
> }
> colnames(pairs) <- cnames.new
> print("pairs=");   print(pairs)
apply(combn(colnames(DF),2), 2, function(x) DF[,x[1]]*DF[,x[2]] )
      [,1] [,2] [,3] [,4] [,5] [,6]
[1,]    0  195  208    0    0  240
[2,]  552  575    0  600    0    0
[3,] 1122    0 1188    0 1224    0
[4,]    0    0    0 1980 2024 2070
[5,] 2862    0 2915    0 2970    0>
>
> nc.tripels <- nc*(nc-1)*(nc-2)/6
> #  initialize vector
> cnames.new <- c(rep("",nc.tripels))
> ind <- 1
> print(sprintf("nc=%d",nc))
> for (i in 1:nc) {
>  if (i+1 <= nc ) {
>    for (j in (i+1):nc) {
>      if (j+1 <= nc ) {
>        for (k in (j+1):nc) {
>          cnames.new[ind] <-  
> paste(cnames[i],cnames[j],cnames[k],sep="")
>          ind <- ind+1
>        }
>      }
>    }
>  }
> }
>
> ind <- 1
> #  initialize data.frame
> tripels <-  
> data.frame(matrix(c(rep(0,nc.tripels*nrow)),ncol=nc.tripels))
> for (i in 1:(nc-1)) {
>  if (i+1 <= nc ) {
>    for (j in (i+1):nc) {
>      if (j+1 <= nc ) {
>        for (k in (j+1):nc) {
>          t <- DF[,i] * DF[,j] * DF[,k]
>          tripels[[ind]] <- t
>          ind <- ind+1
>        }
>      }
>    }
>  }
> }
> colnames(tripels) <-  cnames.new
> print("tripels=");   print(tripels)
 > apply(combn(colnames(DF),3), 2, function(x)  
DF[,x[1]]*DF[,x[2]]*DF[,x[3]])
       [,1]   [,2] [,3]  [,4]
[1,]     0      0 3120     0
[2,] 13800      0    0     0
[3,]     0  40392    0     0
[4,]     0      0    0 91080
[5,]     0 157410    0     0
>
>
> I suppose that here is a much shorter way to get the same results. Any
> hint is very much appreciated.
David Winsemius, MD
Heritage Laboratories
West Hartford, CT

Juergen Rose

2009-Apr-16 16:33 UTC

head link

[R] Howto build combinations of colums of a data frame

Am Donnerstag, den 16.04.2009, 10:59 -0400 schrieb David Winsemius:

Thanks David,

is there also a shorter way to get the columns names of the new data
frames?

Juergen
> On Apr 16, 2009, at 10:14 AM, Juergen Rose wrote:
> 
> > Hi,
> >
> > as a R-newcomer I would like to create some new data frames from a  
> > given
> > data frame. The first new data frame should content all pairs of the
> > columns of the original data frame. The second new data frame should
> > content all tripels of of the columns of the original data frame and  
> > the
> > last the quadrupel of columns. The values in the new data frames  
> > should
> > be the product of two, three our four original single field values.  
> > For
> > pairs and tripels I could realize that task, with the following R
> > script:
> >
> > Lines <- "a    b    c    d
> >    13     0    15   16
> >    23    24    25    0
> >    33    34     0   36
> >     0    44    45   46
> >    53    54     0   55"
> >
> > DF <- read.table(textConnection(Lines), header = TRUE)
> >
> > nrow <-length(rownames(DF))
> > cnames <- colnames(DF)
> > nc <-length(DF)
> >
> > nc.pairs <- nc*(nc-1)/2
> > #  initialize vector
> > cnames.new <- c(rep("",nc.pairs))
> > ind <- 1
> > print(sprintf("nc=%d",nc))
> > for (i in 1:(nc-1)) {
> >  if (i+1 <= nc ) {
> >    for (j in (i+1):nc) {
> >      cnames.new[ind] <- paste(cnames[i],cnames[j],sep="")
> >      ind <- ind+1
> >    }
> >  }
> > }
> >
> > ind <- 1
> > #  initialize data.frame
> > pairs <- data.frame(matrix(c(rep(0,nc.pairs*nrow)),ncol=nc.pairs))
> > for (i in 1:nc) {
> >  if (i+1 <= nc ) {
> >    for (j in (i+1):nc) {
> >      t <- DF[,i] * DF[,j]
> >      pairs[[ind]] <- t
> >      ind <- ind+1
> >    }
> >  }
> > }
> > colnames(pairs) <- cnames.new
> > print("pairs=");   print(pairs)
> 
> apply(combn(colnames(DF),2), 2, function(x) DF[,x[1]]*DF[,x[2]] )
>       [,1] [,2] [,3] [,4] [,5] [,6]
> [1,]    0  195  208    0    0  240
> [2,]  552  575    0  600    0    0
> [3,] 1122    0 1188    0 1224    0
> [4,]    0    0    0 1980 2024 2070
> [5,] 2862    0 2915    0 2970    0
> >
> >
> > nc.tripels <- nc*(nc-1)*(nc-2)/6
> > #  initialize vector
> > cnames.new <- c(rep("",nc.tripels))
> > ind <- 1
> > print(sprintf("nc=%d",nc))
> > for (i in 1:nc) {
> >  if (i+1 <= nc ) {
> >    for (j in (i+1):nc) {
> >      if (j+1 <= nc ) {
> >        for (k in (j+1):nc) {
> >          cnames.new[ind] <-  
> > paste(cnames[i],cnames[j],cnames[k],sep="")
> >          ind <- ind+1
> >        }
> >      }
> >    }
> >  }
> > }
> >
> > ind <- 1
> > #  initialize data.frame
> > tripels <-  
> > data.frame(matrix(c(rep(0,nc.tripels*nrow)),ncol=nc.tripels))
> > for (i in 1:(nc-1)) {
> >  if (i+1 <= nc ) {
> >    for (j in (i+1):nc) {
> >      if (j+1 <= nc ) {
> >        for (k in (j+1):nc) {
> >          t <- DF[,i] * DF[,j] * DF[,k]
> >          tripels[[ind]] <- t
> >          ind <- ind+1
> >        }
> >      }
> >    }
> >  }
> > }
> > colnames(tripels) <-  cnames.new
> > print("tripels=");   print(tripels)
> 
>  > apply(combn(colnames(DF),3), 2, function(x)  
> DF[,x[1]]*DF[,x[2]]*DF[,x[3]])
>        [,1]   [,2] [,3]  [,4]
> [1,]     0      0 3120     0
> [2,] 13800      0    0     0
> [3,]     0  40392    0     0
> [4,]     0      0    0 91080
> [5,]     0 157410    0     0
> 
> >
> >
> > I suppose that here is a much shorter way to get the same results. Any
> > hint is very much appreciated.
> 
> David Winsemius, MD
> Heritage Laboratories
> West Hartford, CT
>

baptiste auguie

2009-Apr-16 16:41 UTC

head link

[R] Howto build combinations of colums of a data frame

Perhaps,

apply(combn(letters[1:4],2), 2, paste,collapse="")

Hope this helps,

baptiste
On 16 Apr 2009, at 17:33, Juergen Rose wrote:
> Am Donnerstag, den 16.04.2009, 10:59 -0400 schrieb David Winsemius:
>
> Thanks David,
>
> is there also a shorter way to get the columns names of the new data
> frames?
>
> Juergen
>
>> On Apr 16, 2009, at 10:14 AM, Juergen Rose wrote:
>>
>>> Hi,
>>>
>>> as a R-newcomer I would like to create some new data frames from a
>>> given
>>> data frame. The first new data frame should content all pairs of
the
>>> columns of the original data frame. The second new data frame
should
>>> content all tripels of of the columns of the original data frame
and
>>> the
>>> last the quadrupel of columns. The values in the new data frames
>>> should
>>> be the product of two, three our four original single field values.
>>> For
>>> pairs and tripels I could realize that task, with the following R
>>> script:
>>>
>>> Lines <- "a    b    c    d
>>>   13     0    15   16
>>>   23    24    25    0
>>>   33    34     0   36
>>>    0    44    45   46
>>>   53    54     0   55"
>>>
>>> DF <- read.table(textConnection(Lines), header = TRUE)
>>>
>>> nrow <-length(rownames(DF))
>>> cnames <- colnames(DF)
>>> nc <-length(DF)
>>>
>>> nc.pairs <- nc*(nc-1)/2
>>> #  initialize vector
>>> cnames.new <- c(rep("",nc.pairs))
>>> ind <- 1
>>> print(sprintf("nc=%d",nc))
>>> for (i in 1:(nc-1)) {
>>> if (i+1 <= nc ) {
>>>   for (j in (i+1):nc) {
>>>     cnames.new[ind] <-
paste(cnames[i],cnames[j],sep="")
>>>     ind <- ind+1
>>>   }
>>> }
>>> }
>>>
>>> ind <- 1
>>> #  initialize data.frame
>>> pairs <-
data.frame(matrix(c(rep(0,nc.pairs*nrow)),ncol=nc.pairs))
>>> for (i in 1:nc) {
>>> if (i+1 <= nc ) {
>>>   for (j in (i+1):nc) {
>>>     t <- DF[,i] * DF[,j]
>>>     pairs[[ind]] <- t
>>>     ind <- ind+1
>>>   }
>>> }
>>> }
>>> colnames(pairs) <- cnames.new
>>> print("pairs=");   print(pairs)
>>
>> apply(combn(colnames(DF),2), 2, function(x) DF[,x[1]]*DF[,x[2]] )
>>      [,1] [,2] [,3] [,4] [,5] [,6]
>> [1,]    0  195  208    0    0  240
>> [2,]  552  575    0  600    0    0
>> [3,] 1122    0 1188    0 1224    0
>> [4,]    0    0    0 1980 2024 2070
>> [5,] 2862    0 2915    0 2970    0
>>>
>>>
>>> nc.tripels <- nc*(nc-1)*(nc-2)/6
>>> #  initialize vector
>>> cnames.new <- c(rep("",nc.tripels))
>>> ind <- 1
>>> print(sprintf("nc=%d",nc))
>>> for (i in 1:nc) {
>>> if (i+1 <= nc ) {
>>>   for (j in (i+1):nc) {
>>>     if (j+1 <= nc ) {
>>>       for (k in (j+1):nc) {
>>>         cnames.new[ind] <-
>>> paste(cnames[i],cnames[j],cnames[k],sep="")
>>>         ind <- ind+1
>>>       }
>>>     }
>>>   }
>>> }
>>> }
>>>
>>> ind <- 1
>>> #  initialize data.frame
>>> tripels <-
>>> data.frame(matrix(c(rep(0,nc.tripels*nrow)),ncol=nc.tripels))
>>> for (i in 1:(nc-1)) {
>>> if (i+1 <= nc ) {
>>>   for (j in (i+1):nc) {
>>>     if (j+1 <= nc ) {
>>>       for (k in (j+1):nc) {
>>>         t <- DF[,i] * DF[,j] * DF[,k]
>>>         tripels[[ind]] <- t
>>>         ind <- ind+1
>>>       }
>>>     }
>>>   }
>>> }
>>> }
>>> colnames(tripels) <-  cnames.new
>>> print("tripels=");   print(tripels)
>>
>>> apply(combn(colnames(DF),3), 2, function(x)
>> DF[,x[1]]*DF[,x[2]]*DF[,x[3]])
>>       [,1]   [,2] [,3]  [,4]
>> [1,]     0      0 3120     0
>> [2,] 13800      0    0     0
>> [3,]     0  40392    0     0
>> [4,]     0      0    0 91080
>> [5,]     0 157410    0     0
>>
>>>
>>>
>>> I suppose that here is a much shorter way to get the same results.
>>> Any
>>> hint is very much appreciated.
>>
>> David Winsemius, MD
>> Heritage Laboratories
>> West Hartford, CT
>>
>
> ______________________________________________
> 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.
_____________________________

Baptiste Augui?

School of Physics
University of Exeter
Stocker Road,
Exeter, Devon,
EX4 4QL, UK

Phone: +44 1392 264187

http://newton.ex.ac.uk/research/emag

Juergen Rose

2009-Apr-16 17:04 UTC

head link

[R] Howto build combinations of colums of a data frame

Am Donnerstag, den 16.04.2009, 17:41 +0100 schrieb baptiste
auguie:> Perhaps,
> 
> apply(combn(letters[1:4],2), 2, paste,collapse="")
> 
> Hope this helps,
Thanks Babtiste,

I use now:

Lines <- "a    b    c    d
    13     0    15   16
    23    24    25    0   
    33    34     0   36
     0    44    45   46
    53    54     0   55"

DF <- read.table(textConnection(Lines), header = TRUE)
cnames <- colnames(DF)

cnames.new  <- apply(combn(cnames,2), 2, paste,collapse="")
pairs <- apply(combn(colnames(DF),2), 2, function(x)
DF[,x[1]]*DF[,x[2]] )
colnames(pairs) <- cnames.new
print("pairs=");   print(pairs)

cnames.new  <- apply(combn(cnames,3), 2, paste,collapse="")
tripels <- apply(combn(colnames(DF),3), 2, function(x)
DF[,x[1]]*DF[,x[2]]*DF[,x[3]])
colnames(tripels) <-  cnames.new
print("tripels=");   print(tripels)

and I am very satisfied.

Juergen
> baptiste
> On 16 Apr 2009, at 17:33, Juergen Rose wrote:
> 
> > Am Donnerstag, den 16.04.2009, 10:59 -0400 schrieb David Winsemius:
> >
> > Thanks David,
> >
> > is there also a shorter way to get the columns names of the new data
> > frames?
> >
> > Juergen
> >
> >> On Apr 16, 2009, at 10:14 AM, Juergen Rose wrote:
> >>
> >>> Hi,
> >>>
> >>> as a R-newcomer I would like to create some new data frames
from a
> >>> given
> >>> data frame. The first new data frame should content all pairs
of the
> >>> columns of the original data frame. The second new data frame
should
> >>> content all tripels of of the columns of the original data
frame and
> >>> the
> >>> last the quadrupel of columns. The values in the new data
frames
> >>> should
> >>> be the product of two, three our four original single field
values.
> >>> For
> >>> pairs and tripels I could realize that task, with the
following R
> >>> script:
> >>>
> >>> Lines <- "a    b    c    d
> >>>   13     0    15   16
> >>>   23    24    25    0
> >>>   33    34     0   36
> >>>    0    44    45   46
> >>>   53    54     0   55"
> >>>
> >>> DF <- read.table(textConnection(Lines), header = TRUE)
> >>>
> >>> nrow <-length(rownames(DF))
> >>> cnames <- colnames(DF)
> >>> nc <-length(DF)
> >>>
> >>> nc.pairs <- nc*(nc-1)/2
> >>> #  initialize vector
> >>> cnames.new <- c(rep("",nc.pairs))
> >>> ind <- 1
> >>> print(sprintf("nc=%d",nc))
> >>> for (i in 1:(nc-1)) {
> >>> if (i+1 <= nc ) {
> >>>   for (j in (i+1):nc) {
> >>>     cnames.new[ind] <-
paste(cnames[i],cnames[j],sep="")
> >>>     ind <- ind+1
> >>>   }
> >>> }
> >>> }
> >>>
> >>> ind <- 1
> >>> #  initialize data.frame
> >>> pairs <-
data.frame(matrix(c(rep(0,nc.pairs*nrow)),ncol=nc.pairs))
> >>> for (i in 1:nc) {
> >>> if (i+1 <= nc ) {
> >>>   for (j in (i+1):nc) {
> >>>     t <- DF[,i] * DF[,j]
> >>>     pairs[[ind]] <- t
> >>>     ind <- ind+1
> >>>   }
> >>> }
> >>> }
> >>> colnames(pairs) <- cnames.new
> >>> print("pairs=");   print(pairs)
> >>
> >> apply(combn(colnames(DF),2), 2, function(x) DF[,x[1]]*DF[,x[2]] )
> >>      [,1] [,2] [,3] [,4] [,5] [,6]
> >> [1,]    0  195  208    0    0  240
> >> [2,]  552  575    0  600    0    0
> >> [3,] 1122    0 1188    0 1224    0
> >> [4,]    0    0    0 1980 2024 2070
> >> [5,] 2862    0 2915    0 2970    0
> >>>
> >>>
> >>> nc.tripels <- nc*(nc-1)*(nc-2)/6
> >>> #  initialize vector
> >>> cnames.new <- c(rep("",nc.tripels))
> >>> ind <- 1
> >>> print(sprintf("nc=%d",nc))
> >>> for (i in 1:nc) {
> >>> if (i+1 <= nc ) {
> >>>   for (j in (i+1):nc) {
> >>>     if (j+1 <= nc ) {
> >>>       for (k in (j+1):nc) {
> >>>         cnames.new[ind] <-
> >>> paste(cnames[i],cnames[j],cnames[k],sep="")
> >>>         ind <- ind+1
> >>>       }
> >>>     }
> >>>   }
> >>> }
> >>> }
> >>>
> >>> ind <- 1
> >>> #  initialize data.frame
> >>> tripels <-
> >>> data.frame(matrix(c(rep(0,nc.tripels*nrow)),ncol=nc.tripels))
> >>> for (i in 1:(nc-1)) {
> >>> if (i+1 <= nc ) {
> >>>   for (j in (i+1):nc) {
> >>>     if (j+1 <= nc ) {
> >>>       for (k in (j+1):nc) {
> >>>         t <- DF[,i] * DF[,j] * DF[,k]
> >>>         tripels[[ind]] <- t
> >>>         ind <- ind+1
> >>>       }
> >>>     }
> >>>   }
> >>> }
> >>> }
> >>> colnames(tripels) <-  cnames.new
> >>> print("tripels=");   print(tripels)
> >>
> >>> apply(combn(colnames(DF),3), 2, function(x)
> >> DF[,x[1]]*DF[,x[2]]*DF[,x[3]])
> >>       [,1]   [,2] [,3]  [,4]
> >> [1,]     0      0 3120     0
> >> [2,] 13800      0    0     0
> >> [3,]     0  40392    0     0
> >> [4,]     0      0    0 91080
> >> [5,]     0 157410    0     0
> >>
> >>>
> >>>
> >>> I suppose that here is a much shorter way to get the same
results.
> >>> Any
> >>> hint is very much appreciated.
> >>
> >> David Winsemius, MD
> >> Heritage Laboratories
> >> West Hartford, CT
> >>
> >
> > ______________________________________________
> > 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.
> 
> _____________________________
> 
> Baptiste Augui?
> 
> School of Physics
> University of Exeter
> Stocker Road,
> Exeter, Devon,
> EX4 4QL, UK
> 
> Phone: +44 1392 264187
> 
> http://newton.ex.ac.uk/research/emag
> ______________________________
>

David Winsemius

2009-Apr-16 17:17 UTC

head link

[R] Howto build combinations of colums of a data frame

Those are not actually dataframes. They are matrices. If you want to  
make them into dataframes, use a coercive function. The names can be  
generated from the original column names using the same construction  
as the column creation:

 > apply(combn(colnames(DF),2), 2, paste, collapse="*")
[1] "a*b" "a*c" "a*d" "b*c"
"b*d" "c*d"
 > apply(combn(colnames(DF),3), 2, paste, collapse="*")
[1] "a*b*c" "a*b*d" "a*c*d" "b*c*d"

-- 
David


On Apr 16, 2009, at 12:33 PM, Juergen Rose wrote:
> Am Donnerstag, den 16.04.2009, 10:59 -0400 schrieb David Winsemius:
>
> Thanks David,
>
> is there also a shorter way to get the columns names of the new data
> frames?
>
> Juergen
>
>> On Apr 16, 2009, at 10:14 AM, Juergen Rose wrote:
>>
>>> Hi,
>>>
>>> as a R-newcomer I would like to create some new data frames from a
>>> given
>>> data frame. The first new data frame should content all pairs of
the
>>> columns of the original data frame. The second new data frame
should
>>> content all tripels of of the columns of the original data frame
and
>>> the
>>> last the quadrupel of columns. The values in the new data frames
>>> should
>>> be the product of two, three our four original single field values.
>>> For
>>> pairs and tripels I could realize that task, with the following R
>>> script:
>>>
>>> Lines <- "a    b    c    d
>>>   13     0    15   16
>>>   23    24    25    0
>>>   33    34     0   36
>>>    0    44    45   46
>>>   53    54     0   55"
>>>
>>> DF <- read.table(textConnection(Lines), header = TRUE)
>>>
>>> nrow <-length(rownames(DF))
>>> cnames <- colnames(DF)
>>> nc <-length(DF)
>>>
>>> nc.pairs <- nc*(nc-1)/2
>>> #  initialize vector
>>> cnames.new <- c(rep("",nc.pairs))
>>> ind <- 1
>>> print(sprintf("nc=%d",nc))
>>> for (i in 1:(nc-1)) {
>>> if (i+1 <= nc ) {
>>>   for (j in (i+1):nc) {
>>>     cnames.new[ind] <-
paste(cnames[i],cnames[j],sep="")
>>>     ind <- ind+1
>>>   }
>>> }
>>> }
>>>
>>> ind <- 1
>>> #  initialize data.frame
>>> pairs <-
data.frame(matrix(c(rep(0,nc.pairs*nrow)),ncol=nc.pairs))
>>> for (i in 1:nc) {
>>> if (i+1 <= nc ) {
>>>   for (j in (i+1):nc) {
>>>     t <- DF[,i] * DF[,j]
>>>     pairs[[ind]] <- t
>>>     ind <- ind+1
>>>   }
>>> }
>>> }
>>> colnames(pairs) <- cnames.new
>>> print("pairs=");   print(pairs)
>>
>> apply(combn(colnames(DF),2), 2, function(x) DF[,x[1]]*DF[,x[2]] )
>>      [,1] [,2] [,3] [,4] [,5] [,6]
>> [1,]    0  195  208    0    0  240
>> [2,]  552  575    0  600    0    0
>> [3,] 1122    0 1188    0 1224    0
>> [4,]    0    0    0 1980 2024 2070
>> [5,] 2862    0 2915    0 2970    0
>>>
>>>
>>> nc.tripels <- nc*(nc-1)*(nc-2)/6
>>> #  initialize vector
>>> cnames.new <- c(rep("",nc.tripels))
>>> ind <- 1
>>> print(sprintf("nc=%d",nc))
>>> for (i in 1:nc) {
>>> if (i+1 <= nc ) {
>>>   for (j in (i+1):nc) {
>>>     if (j+1 <= nc ) {
>>>       for (k in (j+1):nc) {
>>>         cnames.new[ind] <-
>>> paste(cnames[i],cnames[j],cnames[k],sep="")
>>>         ind <- ind+1
>>>       }
>>>     }
>>>   }
>>> }
>>> }
>>>
>>> ind <- 1
>>> #  initialize data.frame
>>> tripels <-
>>> data.frame(matrix(c(rep(0,nc.tripels*nrow)),ncol=nc.tripels))
>>> for (i in 1:(nc-1)) {
>>> if (i+1 <= nc ) {
>>>   for (j in (i+1):nc) {
>>>     if (j+1 <= nc ) {
>>>       for (k in (j+1):nc) {
>>>         t <- DF[,i] * DF[,j] * DF[,k]
>>>         tripels[[ind]] <- t
>>>         ind <- ind+1
>>>       }
>>>     }
>>>   }
>>> }
>>> }
>>> colnames(tripels) <-  cnames.new
>>> print("tripels=");   print(tripels)
>>
>>> apply(combn(colnames(DF),3), 2, function(x)
>> DF[,x[1]]*DF[,x[2]]*DF[,x[3]])
>>       [,1]   [,2] [,3]  [,4]
>> [1,]     0      0 3120     0
>> [2,] 13800      0    0     0
>> [3,]     0  40392    0     0
>> [4,]     0      0    0 91080
>> [5,]     0 157410    0     0
>>
David Winsemius, MD
Heritage Laboratories
West Hartford, CT

R help - Apr 2009 - Howto build combinations of colums of a data frame

[R] Howto build combinations of colums of a data frame

[R] Howto build combinations of colums of a data frame

[R] Howto build combinations of colums of a data frame

[R] Howto build combinations of colums of a data frame

[R] Howto build combinations of colums of a data frame

[R] Howto build combinations of colums of a data frame