R help - Apr 2021 - Assigning several lists to variables whose names are contained in other variables

Dear all,

I'm creating a list (which is a tbl_graph) by a function, and assign the 
result to a variable:

subnet_MYSUBNET <- my_function(MYSUBNET)

# MYSUBNET: a tbl_graph

Because there are multiple subnets to create, I can get the names of the 
subnets (MYSUBNET1, MYSUBNET2, MYSUBNET3, etc.) from a row in a 
dataframe column.

subnet_MYSUBNET <- my_function(datatable$column[i])

Because I know how many subnets to create - nrow(dataframe) I want to 
assign the subnets to variables whose names contain the name of the subnet

For this to work I have to assign a variable name which is contained in 
an other variable name:

#################

for(i in 1:nrow(datatable)) {

val <- datatable$column[i]

result <- assign(paste("subnet_",? val, sep = "")

result <- my_function(val)

}

this works in bash, but seems not to work in R - I don't succeed at least.

Am I wrong?

Where is my mistake?

Many thanks in advance for any hint.

Wolfgang



	[[alternative HTML version deleted]]

Hi


I may be wrong but
> result <- assign(paste("subnet_",  val, sep = "")
here you miss the right parentheses
maybe you intended
assign(result, paste("subnet_",  val, sep = ""))
> result <- my_function(val)
but here you change (rewrite) the result variable to my_function result

So your overall cycle gives you only one result variable containing last value 
computed by my_function.

Cheers
Petr
> -----Original Message-----
> From: R-help <r-help-bounces at r-project.org> On Behalf Of Wolfgang
Grond
> Sent: Friday, April 9, 2021 11:49 AM
> To: mailman, r-help <r-help at r-project.org>
> Subject: [R] Assigning several lists to variables whose names are contained
> in
> other variables
>
> Dear all,
>
> I'm creating a list (which is a tbl_graph) by a function, and assign
the
> result to
> a variable:
>
> subnet_MYSUBNET <- my_function(MYSUBNET)
>
> # MYSUBNET: a tbl_graph
>
> Because there are multiple subnets to create, I can get the names of the
> subnets (MYSUBNET1, MYSUBNET2, MYSUBNET3, etc.) from a row in a
> dataframe column.
>
> subnet_MYSUBNET <- my_function(datatable$column[i])
>
> Because I know how many subnets to create - nrow(dataframe) I want to
> assign the subnets to variables whose names contain the name of the subnet
>
> For this to work I have to assign a variable name which is contained in an
> other variable name:
>
> #################
>
> for(i in 1:nrow(datatable)) {
>
> val <- datatable$column[i]
>
> result <- assign(paste("subnet_",  val, sep = "")
>
> result <- my_function(val)
>
> }
>
> this works in bash, but seems not to work in R - I don't succeed at
least.
>
> Am I wrong?
>
> Where is my mistake?
>
> Many thanks in advance for any hint.
>
> Wolfgang
>
>
>
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
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> PLEASE do read the posting guide http://www.R-project.org/posting-
> guide.html
> and provide commented, minimal, self-contained, reproducible code.

Wolfgang,
> result <- assign(paste("subnet_",? val, sep = "")
> 
> result <- my_function(val)
i don't understand why you are twice assigning to =result=.  also, the
first assignment doesn't seem well formatted (t's missing a value?).

did you mean something like

: assign(paste("subnet_",? val, sep = ""), my_function(val))

(which i would think should work)?

cheers, Greg

Dear Wolfgang,

On Fri, 9 Apr 2021 11:48:55 +0200
Wolfgang Grond <grond at numberland.de> wrote:
> I want to assign the subnets to variables whose names contain the
> name of the subnet
Apologies if this sounds too opinionated, but creating variable names
from variable values is a FAQ in a different dynamic language:

https://perldoc.perl.org/perlfaq7#How-can-I-use-a-variable-as-a-variable-name?

Most of the explanation doesn't apply to R, of course, but the main
idea here is to use data structures instead of causing (potential,
unlikely, but still) conflicts in the variable namespace. What if you
create a list of function values instead of just a bunch of variables?

results <- list()
for(i in 1:nrow(datatable)) {
	val <- datatable$column[i]
	results[[as.character(val)]] <- my_function(val)
}

Or even

results <- lapply(setNames(nm = datatable$column), my_function)

Wouldn't that be more convenient?

-- 
Best regards,
Ivan