assign object with loop (translation from SAS to R)

I have a dataset named DM with p1, p2, ...., p9 (9 columns, numerical values)
I would like to calculate to multify each pair of columns (p1p2, p1p3,...
p1p9, p2p3, p2p4.... p8p9) and assign them in p1p2, p1p3,... p1p9, p2p3,
p2p4.... p8p9

In SAS,

l=0;
p_int_sum=0;	
do i=1 to 8;
	do j=(i+1) to 9;
	l=l+1;
	p{i}p{j}=p{i}*p{j};
	end;
end;

I would like to know how to assign them in R
I tried for function but failed.
for (i in 1:8) {
for (j in 2:9) {
DM$p[i]p[j] <- DM$p[i] * DM$p[j]

}}

Thank you so much for reading this!

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I have a dataset named DM with p1, p2, ...., p9 (9 columns,  
numerical values)
I would like to calculate to multify each pair of columns (p1p2,  
p1p3,...
p1p9, p2p3, p2p4.... p8p9) and assign them in p1p2, p1p3,... p1p9,  
p2p3,
p2p4.... p8p9

In SAS,

l=0;
p_int_sum=0;	
do i=1 to 8;
	do j=(i+1) to 9;
	l=l+1;
	p{i}p{j}=p{i}*p{j};
	end;
end;

I would like to know how to assign them in R
I tried for function but failed.
for (i in 1:8) {
for (j in 2:9) {

DM$p[i]p[j] <- DM$p[i] * DM$p[j]

}}

I have a dataset named DM with p1, p2, ...., p9 (9 columns, numerical
values) I would like to calculate to multify each pair of columns
(p1p2, p1p3,...
p1p9, p2p3, p2p4.... p8p9) and assign them in p1p2, p1p3,... p1p9,
p2p3, p2p4.... p8p9

In SAS,

l=0;
p_int_sum=0;
do i=1 to 8;
      do j=(i+1) to 9;
      l=l+1;
      p{i}p{j}=p{i}*p{j};
      end;
end;

I would like to know how to assign them in R I tried for function but
failed.
for (i in 1:8) {
for (j in 2:9) {

DM$p[i]p[j] <- DM$p[i] * DM$p[j]

}}

# Create some data and label columns
DM <- data.frame(matrix(round(runif(90)*10, 0), ncol=9))
colnames(DM) <- paste0("p", 1:9)

# Create i, j indices and label columns
idx <- expand.grid(2:9, 1:8)
colnames(idx) <- c("j", "i")

# Compute products in DM2 and label columns
DM2 <- DM[idx$i]*DM[idx$j]
colnames(DM2) <- paste0("p", idx$i, "p", idx$j)

# Combine original data with products
DM <- data.frame(DM, DM2)

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
project.org] On Behalf Of ONKELINX, Thierry
Sent: Friday, June 29, 2012 10:11 AM
To: David Winsemius; lynx
Cc: r-help at r-project.org
Subject: Re: [R] assign object with loop (translation from SAS to R)

You can use a combination of the outer() and apply() functions

n <- 10
p <- 9
dataset <- data.frame(matrix(rep(seq_len(p), each = n), nrow = n, ncol
= p))
colnames(dataset) <- paste("p", seq_len(p), sep = "")
test <- t(apply(dataset, 1, function(x){ x %o% x}))
colnames(test) <- paste("p", rep(seq_len(p), each = p), "p",
rep(seq_len(p), p), sep = "")
test <- test[, rep(seq_len(p), each = p) < rep(seq_len(p), p)]



ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek / Research Institute for Nature
and Forest
team Biometrie & Kwaliteitszorg / team Biometrics & Quality Assurance
Kliniekstraat 25
1070 Anderlecht
Belgium
+ 32 2 525 02 51
+ 32 54 43 61 85
Thierry.Onkelinx at inbo.be
www.inbo.be

To call in the statistician after the experiment is done may be no more
than asking him to perform a post-mortem examination: he may be able to
say what the experiment died of.
~ Sir Ronald Aylmer Fisher

The plural of anecdote is not data.
~ Roger Brinner

The combination of some data and an aching desire for an answer does
not ensure that a reasonable answer can be extracted from a given body
of data.
~ John Tukey

-----Oorspronkelijk bericht-----
Van: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
Namens David Winsemius
Verzonden: vrijdag 29 juni 2012 16:18
Aan: lynx
CC: r-help at r-project.org
Onderwerp: Re: [R] assign object with loop (translation from SAS to R)


On Jun 28, 2012, at 9:18 PM, lynx wrote:

I have a dataset named DM with p1, p2, ...., p9 (9 columns, numerical
values) I would like to calculate to multify each pair of columns
(p1p2, p1p3,...
p1p9, p2p3, p2p4.... p8p9) and assign them in p1p2, p1p3,... p1p9,
p2p3, p2p4.... p8p9

In SAS,

l=0;
p_int_sum=0;
do i=1 to 8;
      do j=(i+1) to 9;
      l=l+1;
      p{i}p{j}=p{i}*p{j};
      end;
end;

I would like to know how to assign them in R I tried for function but
failed.
for (i in 1:8) {
for (j in 2:9) {

# Try instead:

DM[[ paste("p",i, "p",j,sep="") ]] <-
           DM[[paste("p",i, sep="")]] * DM[[paste("p",i, sep="")]]

DM$p[i]p[j] <- DM$p[i] * DM$p[j]

}}

I suspect there is a more elegant method than this use of R as a macro
processor. I tested the above approach with suitably smalled subscripts
on a smaller dataset:

DM <- data.frame(p1=1:10,p2=1:10,p3=1:10,p4=1:10,p5=1:10)


--
David Winsemius, MD
West Hartford, CT