R: Passing Column Names to Function w/ dplyr - r

Question

I am trying to set up a function in R which prepares data in a specific format to be fed into a correlogram. When manipulating datasets I tend to use dplyr due to its clarity and ease of use, but I am running into problems trying to pass a dataset and specified column names into this function while using dplyr.
This is the set up, included here (in slightly abbreviated form) for clarity. I have not encountered any errors with this and before posting this I confirmed corrData is set up properly:
library(corrplot)
library(tidyverse)
library(stringr)
table2a <- table2 %>%
mutate(example_index = str_c(country,year, sep="."))
Here is the actual function:
prepCorr <- function(dtable, x2, index2) {
practice <- dtable %>%
select(index2, x2) %>%
mutate(count=1) %>%
complete(index2, x2)
practice$count[is.na(practice$count)] <- 0
practice <- spread(practice, key = x2, value = count)
M <- cor(practice)
return(M)
}
prepCorr(table2a, type, example_index)
Whenever I run this function I get:
Error in overscope_eval_next(overscope, expr) : object 'example_index' not found
I have also tried to take advantage of quosures to fix this, but recieve a different error when I do so. When I run the following modified code:
prepCorr <- function(dtable, x2, index2) {
x2 <- enquo(x2)
index2 <- enquo(index2)
practice <- dtable %>%
select(!!index2, !!x2) %>%
mutate(count=1) %>%
complete(!!index2, !!x2)
practice$count[is.na(practice$count)] <- 0
practice <- spread(practice, key = !!x2, value = count)
return(cor(practice))
}
prepCorr(table2a, type, example_index)
I get:
Error in !index2 : invalid argument type
What am I doing wrong here, and how can I fix this? I believe I am using dplyr 0.7 for clarification.
UPDATE: replaced old example with reproducible example.

Answer 1

Look at this example
library(dplyr)
myfun <- function(df, col1, col2) {
col1 <- enquo(col1) # need to quote
col2 <- enquo(col2)
df1 <- df %>%
select(!!col1, !!col2) #!! unquotes
return(df1)
}
myfun(mtcars, cyl, gear)
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