R help - Aug 2010 - How to name matrices from a list with lapply ?

Dear list,

I have a list of matrices :

i1 <- matrix(1:10, nrow = 2, ncol = 5)
i2 <- matrix(11:20, nrow = 2, ncol = 5)
j <- list(i1 = i1, i2 = i2)

I would like to attribute names to each dimension, for each matrix,
as follows :

$i1
B1 B2 B3 B4 B5
A1 1 3 5 7 9
A2 2 4 6 8 10

$i2
B1 B2 B3 B4 B5
A1 11 13 15 17 19
A2 12 14 16 18 20

However, I have to use lapply function and attribute names
after declaration of j, like this :

names <- list(c("A1", "A2"), c("B1",
"B2", "B3", "B4", "B5"))
lapply(j, function (x) {dimnames(x) <- names})
or
lapply(j, function (x) {as.matrix(x, dimnames = names)})

But, it does not work.

I can use : lapply(j, function (x) {matrix(x, nrow = 2, ncol = 5, dimnames
names)})

But, I think a better way exists ...

Thanks in advance,
Carlos

	[[alternative HTML version deleted]]

Hi Carlos,

Look at this:

i1 <- matrix(1:10, nrow = 2, ncol = 5)
i2 <- matrix(11:20, nrow = 2, ncol = 5)
j <- list(i1 = i1, i2 = i2)
my.names <- list(c("A1", "A2"), c("B1",
"B2", "B3", "B4", "B5"))

j.new <- lapply(j, function (x) {dimnames(x) <- my.names; return(x)})
j.new

the issue was just that you have to save the output from lapply.

Cheers,

Josh

On Tue, Aug 3, 2010 at 8:42 AM, Carlos Petti <carlos.petti at gmail.com>
wrote:
> Dear list,
>
> I have a list of matrices :
>
> i1 <- matrix(1:10, nrow = 2, ncol = 5)
> i2 <- matrix(11:20, nrow = 2, ncol = 5)
> j <- list(i1 = i1, i2 = i2)
>
> I would like to attribute names to each dimension, for each matrix,
> as follows :
>
> $i1
> B1 B2 B3 B4 B5
> A1 1 3 5 7 9
> A2 2 4 6 8 10
>
> $i2
> B1 B2 B3 B4 B5
> A1 11 13 15 17 19
> A2 12 14 16 18 20
>
> However, I have to use lapply function and attribute names
> after declaration of j, like this :
>
> names <- list(c("A1", "A2"), c("B1",
"B2", "B3", "B4", "B5"))
> lapply(j, function (x) {dimnames(x) <- names})
> or
> lapply(j, function (x) {as.matrix(x, dimnames = names)})
>
> But, it does not work.
>
> I can use : lapply(j, function (x) {matrix(x, nrow = 2, ncol = 5, dimnames
> names)})
>
> But, I think a better way exists ...
>
> Thanks in advance,
> Carlos
>
> ? ? ? ?[[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.
>


-- 
Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles
http://www.joshuawiley.com/

On Tue, Aug 3, 2010 at 11:42 AM, Carlos Petti <carlos.petti at gmail.com>
wrote:
> Dear list,
>
> I have a list of matrices :
>
> i1 <- matrix(1:10, nrow = 2, ncol = 5)
> i2 <- matrix(11:20, nrow = 2, ncol = 5)
> j <- list(i1 = i1, i2 = i2)
>
> I would like to attribute names to each dimension, for each matrix,
> as follows :
>
> $i1
> B1 B2 B3 B4 B5
> A1 1 3 5 7 9
> A2 2 4 6 8 10
>
> $i2
> B1 B2 B3 B4 B5
> A1 11 13 15 17 19
> A2 12 14 16 18 20
>
> However, I have to use lapply function and attribute names
> after declaration of j, like this :
>
> names <- list(c("A1", "A2"), c("B1",
"B2", "B3", "B4", "B5"))
> lapply(j, function (x) {dimnames(x) <- names})
> or
> lapply(j, function (x) {as.matrix(x, dimnames = names)})
>
> But, it does not work.
>
> I can use : lapply(j, function (x) {matrix(x, nrow = 2, ncol = 5, dimnames
> names)})
>
Try this:

   lapply(j, structure, dimnames = names)