Calling function throws error / running lines manually does not

Question

Ok, I am struggling a bit to find the proper way to describe my issue. Sorry if it is a dumb question, I am still learning.

I have a series of small data.frames named regularly "CountX_YYYY" (X stands for a specific case, YYYY stands for a given year). I have written a function that starts by getting a certain type (X) of them, binding them all and cleaning the id (year), like the one below:

library(dplyr)

analysis <- function(case_pattern){

  cases <- mget(ls(pattern = case_pattern)) %>%
    bind_rows(.id = "id") %>%
    rename(year = id) %>%
    mutate(year = str_sub(year,-4))

  return(cases)
}

Where the case_pattern used is, for example, "^Count1"

It is a fairly simple code, and if I run the body of the function manually, as done below, it works normally:

case_pattern <- "^Count1"

cases <- mget(ls(pattern = case_pattern)) %>%
    bind_rows(.id = "id") %>%
    rename(year = id) %>%
    mutate(year = str_sub(year,-4))

However, if I do the exact same thing by calling the function:

case_pattern <- "^Count1"
analysis(case_pattern)

It throws out the following error:

Error: This tidyselect interface doesn't support predicates yet.
i Contact the package author and suggest using `eval_select()`.

(Below, the traceback, I dont know if it helps)

29.
stop(fallback) 
28.
signal_abort(cnd) 
27.
abort(c("This tidyselect interface doesn't support predicates yet.", 
    i = "Contact the package author and suggest using `eval_select()`.")) 
26.
as_indices_sel_impl(out, vars = vars, strict = strict, data) 
25.
walk_data_tree(new, data_mask, context_mask) 
24.
reduce_sels(node, data_mask, context_mask, init = init) 
23.
eval_c(expr, data_mask, context_mask) 
22.
walk_data_tree(expr, data_mask, context_mask) 
21.
vars_select_eval(vars, expr, strict, data = x, name_spec = name_spec, 
    uniquely_named = uniquely_named, type = type) 
20.
withCallingHandlers(expr, simpleError = function(cnd) {
    abort(conditionMessage(cnd), parent = cnd)
}) 
19.
instrument_base_errors(expr) 
18.
doTryCatch(return(expr), name, parentenv, handler) 
17.
tryCatchOne(expr, names, parentenv, handlers[[1L]]) 
16.
tryCatchList(expr, classes, parentenv, handlers) 
15.
tryCatch(instrument_base_errors(expr), vctrs_error_subscript = function(cnd) {
    cnd$subscript_action <- subscript_action(type)
    cnd$subscript_elt <- "column"
    cnd_signal(cnd) ... 
14.
with_subscript_errors(vars_select_eval(vars, expr, strict, data = x, 
    name_spec = name_spec, uniquely_named = uniquely_named, type = type), 
    type = type) 
13.
eval_select_impl(x, names, {
    {
        sel
    } ... 
12.
rename_impl(NULL, .vars, quo(c(...)), strict = .strict) 
11.
tidyselect::vars_rename(names(.data), !!!enquos(...)) 
10.
rename.data.frame(., year = id) 
9.
rename(., year = id) 
8.
function_list[[i]](value) 
7.
freduce(value, `_function_list`) 
6.
`_fseq`(`_lhs`) 
5.
eval(quote(`_fseq`(`_lhs`)), env, env) 
4.
eval(quote(`_fseq`(`_lhs`)), env, env) 
3.
withVisible(eval(quote(`_fseq`(`_lhs`)), env, env)) 
2.
mget(ls(pattern = case_pattern)) %>% bind_rows(.id = "id") %>% 
    rename(year = id) %>% mutate(year = str_sub(year, -4))
1.
analysis(case_pattern)

I have not been able to identify/understand this error, but it seems to me that both ways should give the same output. Isn't?

Anyway, thanks in advance!

Answer 1

The issue seems to be stemming from the envir in the ls and mget because mget inside the function is looking for the objects inside that function env

library(dplyr)
analysis <- function(case_pattern) {
    mget(ls(pattern = case_pattern)) %>%
    bind_rows(.id = 'id')
   }
Count1 <- head(mtcars)
Count2 <- head(mtcars)
analysis("^Count\\d+$")
#data frame with 0 columns and 0 rows

We can specify the envir to .GlobalEnv and it should work

analysis <- function(case_pattern) {
   mget(ls(pattern = case_pattern, envir = .GlobalEnv), envir = .GlobalEnv)  %>% 
        bind_rows(.id = 'id')
}
analysis("^Count\\d+$")
#                            id  mpg cyl disp  hp drat    wt  qsec vs am gear carb
#Mazda RX4...1          Count1 21.0   6  160 110 3.90 2.620 16.46  0  1    4    4
#Mazda RX4 Wag...2      Count1 21.0   6  160 110 3.90 2.875 17.02  0  1    4    4
#Datsun 710...3         Count1 22.8   4  108  93 3.85 2.320 18.61  1  1    4    1
#Hornet 4 Drive...4     Count1 21.4   6  258 110 3.08 3.215 19.44  1  0    3    1
#Hornet Sportabout...5  Count1 18.7   8  360 175 3.15 3.440 17.02  0  0    3    2
# ...