Skip to content

loop for column substraction of a matrix

6 messages · arun, Eliza Botto, Rui Barradas

Rui Barradas
# 
Hello,

1. Let me refrase it a bit. For each column, sum all others and take the 
symmetric.


mat <- matrix(1:30, ncol = 3)
sapply(seq_len(ncol(mat)), function(i) -rowSums(mat[, -i]))


2. write.table (maybe using sep = "\t" ?) and send the file to printer.

Hope this helps,

Rui Barradas

Em 05-10-2012 21:05, eliza botto escreveu:
arun
# 
HI,

Try this:
set.seed(1)
?mat1<-matrix(sample(1:500,380,replace=TRUE),ncol=38)
list1<-list()
for(i in 1:ncol(mat1)){
?list1[[i]]<-t(apply(mat1,1,function(x) x[i]-x))
?list1}


list1
A.K.


----- Original Message -----
From: eliza botto <eliza_botto at hotmail.com>
To: "r-help at r-project.org" <r-help at r-project.org>
Cc: 
Sent: Friday, October 5, 2012 4:05 PM
Subject: [R] loop for column substraction of a matrix


Dear useRs,


I have a matrix with 38 columns and 365 rows. what i want to do is the following.....

1. subtracting from each column, first itself and then all the remaining columns. More precisely, from column number 1, i will first subtract itself(column 1) and then the remaining 37 columns. Afterwards i will take column number 2 and do the same. In this way i want to proceed till 38th column. 
2. i want to print the resulting matrix on A4 paper.

Bundle of thanks in advance.

best regards
eliza


??? ???  ??? ?  ??? ??? ? 
??? [[alternative HTML version deleted]]

______________________________________________
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.
arun
# 
Hi,

Sorry, I think I misunderstand your question (after reading Rui's solution).

You can also try any of these to get the result if this is what you meant:
set.seed(1)
mat1<-matrix(sample(1:500,380,replace=TRUE),ncol=38)
res1<-t(do.call(rbind,lapply(1:ncol(mat1), function(i) mat1[,i]-apply(mat1,1,sum))))
#or
res1<-sapply(1:ncol(mat1), function(i) mat1[,i]-apply(mat1,1,sum))
#or
res1<-mapply(FUN=function(i) mat1[,i]-rowSums(mat1), 1:ncol(mat1))
A.K? 





----- Original Message -----
From: eliza botto <eliza_botto at hotmail.com>
To: "r-help at r-project.org" <r-help at r-project.org>
Cc: 
Sent: Friday, October 5, 2012 4:05 PM
Subject: [R] loop for column substraction of a matrix


Dear useRs,


I have a matrix with 38 columns and 365 rows. what i want to do is the following.....

1. subtracting from each column, first itself and then all the remaining columns. More precisely, from column number 1, i will first subtract itself(column 1) and then the remaining 37 columns. Afterwards i will take column number 2 and do the same. In this way i want to proceed till 38th column. 
2. i want to print the resulting matrix on A4 paper.

Bundle of thanks in advance.

best regards
eliza


??? ???  ??? ?  ??? ??? ? 
??? [[alternative HTML version deleted]]

______________________________________________
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.
Rui Barradas
# 
Or, using your mapply solution, compute

rs <- rowSums(mat1)

and then use it for all subtractions. With a larger dataset this would 
be probably faster.

Rui Barradas
Em 05-10-2012 22:41, arun escreveu: