[R] Write columns from within a list to a matrix?
Hello,
I think I have a mental block when it comes to working with lists. lapply and
sapply appear to do some magical things, but I can't seem to master their usage.
As an example, I would like to convert a column within a list to a matrix, with
the list element corresponding to the new matrix column.
#Here is a simplified example: .
test=vector(list, 3)
for (i in 1:3){ test[[i]]=cbind(runif(15), rnorm(15,2)) } #create example list
(I'm sure there is a better way to do this too).
#Now, I wan to get the second column back out, converting it from a list to a
matrix. This works, but gets confusing/inefficient when I have multiple
complex lists I am trying to manage.
savecol2=matrix(0,15,0)
for (i in 1:3){
savecol2=cbind(savecol2, test[[i]][,1])
}
#Something like??: (of course this doesn't work)
savecol2=sapply(test, [[, function(x) x[2,])
Thank you!
Jeff
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Re: [R] Write columns from within a list to a matrix?
test - lapply(1:3, function(i) cbind(runif(15), rnorm(15,2)))
sapply(test, [, 16:30)
b
On Jul 22, 2007, at 3:39 PM, [EMAIL PROTECTED] wrote:
Hello,
I think I have a mental block when it comes to working with lists.
lapply and sapply appear to do some magical things, but I can't
seem to master their usage.
As an example, I would like to convert a column within a list to a
matrix, with the list element corresponding to the new matrix column.
#Here is a simplified example: .
test=vector(list, 3)
for (i in 1:3){ test[[i]]=cbind(runif(15), rnorm(15,2)) } #create
example list (I'm sure there is a better way to do this too).
#Now, I wan to get the second column back out, converting it from a
list to a matrix. This works, but gets confusing/inefficient when
I have multiple complex lists I am trying to manage.
savecol2=matrix(0,15,0)
for (i in 1:3){
savecol2=cbind(savecol2, test[[i]][,1])
}
#Something like??: (of course this doesn't work)
savecol2=sapply(test, [[, function(x) x[2,])
Thank you!
Jeff
__
R-help@stat.math.ethz.ch 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@stat.math.ethz.ch 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.
Re: [R] Write columns from within a list to a matrix?
oh! and if you want to be less ad-hoc:
sapply(test, function(x) x[,2])
b
On Jul 22, 2007, at 3:50 PM, Benilton Carvalho wrote:
test - lapply(1:3, function(i) cbind(runif(15), rnorm(15,2)))
sapply(test, [, 16:30)
b
On Jul 22, 2007, at 3:39 PM, [EMAIL PROTECTED] wrote:
Hello,
I think I have a mental block when it comes to working with
lists. lapply and sapply appear to do some magical things, but I
can't seem to master their usage.
As an example, I would like to convert a column within a list to a
matrix, with the list element corresponding to the new matrix column.
#Here is a simplified example: .
test=vector(list, 3)
for (i in 1:3){ test[[i]]=cbind(runif(15), rnorm(15,2)) } #create
example list (I'm sure there is a better way to do this too).
#Now, I wan to get the second column back out, converting it from
a list to a matrix. This works, but gets confusing/inefficient
when I have multiple complex lists I am trying to manage.
savecol2=matrix(0,15,0)
for (i in 1:3){
savecol2=cbind(savecol2, test[[i]][,1])
}
#Something like??: (of course this doesn't work)
savecol2=sapply(test, [[, function(x) x[2,])
Thank you!
Jeff
__
R-help@stat.math.ethz.ch 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@stat.math.ethz.ch 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.
Re: [R] Write columns from within a list to a matrix?
Very close... Actually it's more like
savecol2=sapply(test, function(x) x[,1])
to get the same matrix as you showed in your for-loop (did you actually want
the first or second column?).
when I have multiple complex lists I am trying to manage...
for this, you can try mapply() which goes something like
mapply(function(x,y) #...function body...#,
x=list1,y=list2)
--- [EMAIL PROTECTED] wrote:
Hello,
I think I have a mental block when it comes to working with lists. lapply
and sapply appear to do some magical things, but I can't seem to master
their usage.
As an example, I would like to convert a column within a list to a matrix,
with the list element corresponding to the new matrix column.
#Here is a simplified example: .
test=vector(list, 3)
for (i in 1:3){ test[[i]]=cbind(runif(15), rnorm(15,2)) } #create example
list (I'm sure there is a better way to do this too).
#Now, I wan to get the second column back out, converting it from a list to
a matrix. This works, but gets confusing/inefficient when I have multiple
complex lists I am trying to manage.
savecol2=matrix(0,15,0)
for (i in 1:3){
savecol2=cbind(savecol2, test[[i]][,1])
}
#Something like??: (of course this doesn't work)
savecol2=sapply(test, [[, function(x) x[2,])
Thank you!
Jeff
__
R-help@stat.math.ethz.ch 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@stat.math.ethz.ch 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.
