R lapply function with two arguments that are not fixed - r

Question

I found a similar question asked before. My question is a bit more complex than the previous one. For my question, the y parameter is not fixed.
In the function(X,Y){SOME FUNCTION}, X is a list of characters and Y is a list of dataframe. Basically, I want the function to work on the pair of X and Y in sequence respectively, and produce the output as one list. For example, the first element of X list and the first element of Y list, the second element of X list and the second element of Y list, the third element of X list and the third element of Y list,...
Example of X, Y
X <- c("1", "2")
y1 <- data.frame("person.1" = "Amy", "bestfood..1" = "fish", "bestthing..1" = "book",
"person.2" = "Mike", "bestfood..2" = "fish", "bestthing..2" = "book")
y2 <- data.frame("person.1" = "Amy","bestfood..1" = "carrot", "bestthing..1" = "cloth",
"person.2" = "Mike","bestfood..2" = "carrot", "bestthing..2" = "cloth")
Y <- list(y1,y2)
The function:
addID <- function(X, Y) {
rowlength <- length(Y)
df <- as.data.frame(matrix(NA, nrow = rowlength, ncol = 3))
colnames(df) <- c("ID", "Person", "Food")
df[1:nrow(df), 1] <- X
# name
namecols <-grep("person",colnames(Y))
for (i in 1:length(namecols)) {
name <- Y[1, namecols[i]]
df[i, 2] <- as.character(name)
}
# food
foodcols <-
grep("bestfood",colnames(Y))
for (i in 1:length(foodcols)) {
food <- Y[1, foodcols[i]]
df[i, 3] <- as.character(foodcols)
}
return(df)
}
}
I tried to use lapply but can't figure out the way to include the X list. When I try this:
lapply(Y, function, X=X)
The function doesn't work properly. I wonder if there are other ways to include X in it(I tried the function on individual character and dataframe, it works just fine. )
I hope this is clear. If not, please point it out, I will try my best to clarify. Thanks in advance.
UPDATE:
I tried Map as suggested by comments. It returns: incorrect number of dimensions. I added some details in the function. It seems like R stucks on the last line.
outcome <- Map(addID, Y, X)
I get
error in Y[1, namecols[i]] : incorrect number of dimensions
In addition: Warning message:
In `[<-.data.frame`(`*tmp*`, 1:nrow(df), 1, value = list(person.1 = 1L, :
provided 6 variables to replace 1 variables
The outcome should looks like:
z1 <- data.frame(ID = c(1,2), Person = c("Amy","Mike"), Food = c("fish", "fish"))
z2 <- data.frame(ID = c(1,2), Person = c("Amy","Mike"), Food = c("carrot", "carrot"))
outcome <- list(z1,z2)

Answer 1

We could do this easily in tidyverse
library(dplyr)
library(tidyr)
bind_rows(Y, .id = 'ID') %>%
select(ID, starts_with('person'), contains('food')) %>%
pivot_longer(cols = -ID, names_to = c(".value"),
names_pattern = "([^.]+)\\.+\\d+")
-output
# A tibble: 4 x 3
ID person bestfood
<chr> <chr> <chr>
1 1 Amy fish
2 1 Mike fish
3 2 Amy carrot
4 2 Mike carrot
With the OP's function, if we modify, it would work
addID <- function(X, Y) {
rowlength <- length(Y)
df <- as.data.frame(matrix(NA, nrow = rowlength, ncol = 3))
colnames(df) <- c("ID", "Person", "Food")
df[1:nrow(df), 1] <- X
namecols <- grep("person",colnames(Y))
df[, 2] <- unlist(Y[namecols])
foodcols <- grep("bestfood", colnames(Y))
df[,3] <- unlist(Y[foodcols])
return(unique(df))
}
-testing
Map(addID, X, Y)
$`1`
ID Person Food
1 1 Amy fish
2 1 Mike fish
$`2`
ID Person Food
1 2 Amy carrot
2 2 Mike carrot