Combine ifelse two conditions and loop - r

Question

I have a liste of dataframes (file1, file2, ..., file 72). For each dataframe I want to create one variable containing information from another dataframe based on two conditions.
The idea is simple:
condition 1: if file*$countryid equals source$country, and
condition 2: if file*$year is higher than source$starting but lower than source$ending, then if true I want to create a column file*$rank with the value in source$rank
I have been trying code lines like this but this code does not go through all lines in source:
file1$rank<-ifelse(file1$countryid=source$countryid & file1$year>source$starting & file1$year<source$ending,source$rank,NA)
In addition I would like to implement this within a loop to avoid iterating manually through all these dataframes:
dflist<-Filter(is.data.frame, mget(ls()))
dflist<-function(df,x){df$rank<-ifelse(df$countryid=source$countryid & df$year>source$starting & df$year<source$ending,source$rank,NA))
Here is an example of the data I have.
Thank you!
> dput(file1)
structure(list(id = c(1, 2, 3), countryid = c(10, 10, 13), year = c(1948,
1954, 1908)), row.names = c(NA, -3L), class = c("tbl_df", "tbl",
"data.frame"))
dput(file2)
structure(list(id = c(1, 2, 3), countryid = c(13, 10, 13), year = c(1907,
1908, 1907)), row.names = c(NA, -3L), class = c("tbl_df", "tbl",
"data.frame"))
> dput(source)
structure(list(country = c(13, 13, 13, 10, 10, 10), rank = c(1,
2, 3, 1, 2, 3), starting = c(1885, 1909, 1940, 1902, 1907, 1931
), ending = c(1908, 1939, 1960, 1906, 1930, 1960)), row.names = c(NA,
-6L), class = c("tbl_df", "tbl", "data.frame"))

Answer 1

We can use a non-equi join after getting all the file\\d+ datasets into a list
library(data.table)
out <- lapply(mget(ls(pattern = '^file\\d+$')), function(dat)
setDT(dat)[, year := as.integer(year)][as.data.table(source), rank := i.rank,
on = .(countryid = country, year > starting, year < ending)])
-output
out
#$file1
# id countryid year rank
#1: 1 10 1948 3
#2: 2 10 1954 3
#3: 3 13 1908 NA
#$file2
# id countryid year rank
#1: 1 13 1907 1
#2: 2 10 1908 2
#3: 3 13 1907 1
if it needs to update the original objects, use list2env
list2env(out, .GlobalEnv)