Create variable based on other variable outside function - r

Question

I'm trying to make my code general, I'd only want to change the YEAR variable without having to change everything in the code
YEAR = 1970
y <- data.frame(col1 = c(1:5))
function (y){
summarize(column_YEAR = sum(col1))
}
#Right now this gives
column_YEAR
1 15
#I would like this function to output this (so col1 is changed to column_1970)
column_1970
1 15
or for example this
df <- list("a_YEAR" = anotherdf)
#I would like to have a list with a df with the name a_1970
I tried things like
df <- list(assign(paste0(a_, YEAR), anotherdf))
But it does not work, does somebody have any advice? Thanks in advance :)

Answer 1

rlang provides a flexible way to defuse R expressions. You can use that functionality to create dynamic column names within dplyr flow. In this example dynamic column name is created using suffix argument passed to a wrapper function on dplyr's summarise.
library("tidyverse")
YEAR = 1970
y <- data.frame(col1 = c(1:5))
function (y) {
summarize(column_YEAR = sum(col1))
}
my_summarise <- function(.data, suffix, sum_col) {
var_name <- paste0("column_", suffix)
summarise(.data,
{{var_name}} := sum({{sum_col}}))
}
my_summarise(.data = y, suffix = YEAR, sum_col = col1)
Results
my_summarise(.data = y, suffix = YEAR, sum_col = col1)
# column_1970
# 1 15
You can also source arguments directly from global environment but from readability perspective this is poorer solution as it's not immediately clear how the function creates suffix.
my_summarise_two <- function(.data, sum_col) {
var_name <- paste0("column_", YEAR)
summarise(.data,
{{var_name}} := sum({{sum_col}}))
}
my_summarise_two(.data = y, sum_col = col1)