Convert object name to string in function - r

Question

I have a list of data.frames. I want to send each data.frame to a function using lapply. Inside the function I want to check whether the name of a data.frame includes a particular string. If the string in question is present I want to perform one series of operations. Otherwise I want to perform a different series of operations. I cannot figure out how to check whether the string in question is present from within the function.
I wish to use base R. This seems to be a possible solution but I cannot get it to work:
In R, how to get an object's name after it is sent to a function?
Here is an example list followed by an example function further below.
matrix.apple1 <- read.table(text = '
X3 X4 X5
1 1 1
1 1 1
', header = TRUE)
matrix.apple2 <- read.table(text = '
X3 X4 X5
1 1 1
2 2 2
', header = TRUE)
matrix.orange1 <- read.table(text = '
X3 X4 X5
10 10 10
20 20 20
', header = TRUE)
my.list <- list(matrix.apple1 = matrix.apple1,
matrix.orange1 = matrix.orange1,
matrix.apple2 = matrix.apple2)
This operation can check whether each object name contains the string apples
but I am not sure how to use this information inside the function further below.
grepl('apple', names(my.list), fixed = TRUE)
#[1] TRUE FALSE TRUE
Here is an example function. Based on hours of searching and trial-and-error I perhaps am supposed to use deparse(substitute(x)) but so far it only returns x or something similar.
table.function <- function(x) {
# The three object names are:
# 'matrix.apple1', 'matrix.orange1' and 'matrix.apple2'
myObjectName <- deparse(substitute(x))
print(myObjectName)
# perform a trivial example operation on a data.frame
my.table <- table(as.matrix(x))
# Test whether an object name contains the string 'apple'
contains.apple <- grep('apple', myObjectName, fixed = TRUE)
# Use the result of the above test to perform a trivial example operation.
# With my code 'my.binomial' is always given the value of 0 even though
# 'apple' appears in the name of two of the data.frames.
my.binomial <- ifelse(contains.apple == 1, 1, 0)
return(list(my.table = my.table, my.binomial = my.binomial))
}
table.function.output <- lapply(my.list, function(x) table.function(x))
These are the results of print(myObjectName):
#[1] "x"
#[1] "x"
#[1] "x"
table.function.output
Here are the rest of the results of table.function showing that my.binomial is always 0.
The first and third value of my.binomial should be 1 because the names of the first and third data.frames contain the string apple.
# $matrix.apple1
# $matrix.apple1$my.table
# 1
# 6
# $matrix.apple1$my.binomial
# logical(0)
#
# $matrix.orange1
# $matrix.orange1$my.table
# 10 20
# 3 3
# $matrix.orange1$my.binomial
# logical(0)
#
# $matrix.apple2
# $matrix.apple2$my.table
# 1 2
# 3 3
# $matrix.apple2$my.binomial
# logical(0)

Answer 1

You could redesign your function to use the list names instead:
table_function <- function(myObjectName) {
# The three object names are:
# 'matrix.apple1', 'matrix.orange1' and 'matrix.apple2'
myObject <- get(myObjectName)
print(myObjectName)
# perform a trivial example operation on a data.frame
my.table <- table(as.matrix(myObject))
# Test whether an object name contains the string 'apple'
contains.apple <- grep('apple', myObjectName, fixed = TRUE)
# Use the result of the above test to perform a trivial example operation.
# With my code 'my.binomial' is always given the value of 0 even though
# 'apple' appears in the name of two of the data.frames.
my.binomial <- +(contains.apple == 1)
return(list(my.table = my.table, my.binomial = my.binomial))
}
lapply(names(my.list), table_function)
This returns
[[1]]
[[1]]$my.table
1
6
[[1]]$my.binomial
[1] 1
[[2]]
[[2]]$my.table
10 20
3 3
[[2]]$my.binomial
integer(0)
[[3]]
[[3]]$my.table
1 2
3 3
[[3]]$my.binomial
[1] 1
If you want to keep the list names, you could use
sapply(names(my.list), table_function, simplify = FALSE, USE.NAMES = TRUE)
instead of lapply.

Answer 2

Use Map and pass both list data and it's name to the function. Change your function to accept two arguments.
table.function <- function(data, name) {
# The three object names are:
# 'matrix.apple1', 'matrix.orange1' and 'matrix.apple2'
print(name)
# perform a trivial example operation on a data.frame
my.table <- table(as.matrix(data))
# Test whether an object name contains the string 'apple'
contains.apple <- grep('apple', name, fixed = TRUE)
# Use the result of the above test to perform a trivial example operation.
# With my code 'my.binomial' is always given the value of 0 even though
# 'apple' appears in the name of two of the data.frames.
my.binomial <- as.integer(contains.apple == 1)
return(list(my.table = my.table, my.binomial = my.binomial))
}
Map(table.function, my.list, names(my.list))
#[1] "matrix.apple1"
#[1] "matrix.orange1"
#[1] "matrix.apple2"
#$matrix.apple1
#$matrix.apple1$my.table
#1
#6
#$matrix.apple1$my.binomial
#[1] 1
#$matrix.orange1
#$matrix.orange1$my.table
#10 20
# 3 3
#$matrix.orange1$my.binomial
#integer(0)
#...
#...
The same functionality is provided by imap in purrr where you don't need to explicitly pass the names.
purrr::imap(my.list, table.function)