R: Passing Column Names to Function w/ dplyr

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.

Would it be alright if I edited the question to use table2 from the tidyverse package rather than the tables shown here? It should work for this purpose nicely. — Josh Kraushaar
– Josh Kraushaar, Commented Aug 22, 2017 at 20:32
Sure, as long as it gives the same error and we can use it to "debug" — csgroen
– csgroen, Commented Aug 22, 2017 at 20:34
Ok, it should be reproducible now, thank you for the pointer. — Josh Kraushaar
– Josh Kraushaar, Commented Aug 22, 2017 at 20:48
Save the RStudio for RStudio-speific problems. (The RStudio interface, or code that works in RGui or on the R command line, but not in RStudio.) — Gregor Thomas
– Gregor Thomas, Commented Aug 22, 2017 at 21:24

CPak · Accepted Answer · 2017-08-22 20:31:40Z

2

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)

You can learn more here link about NSE vs SE

answered Aug 22, 2017 at 20:31

CPak

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6 Comments

Josh Kraushaar Over a year ago

When I run that, using say index2 <- enquo(index2) I keep getting: ** "Error in !index2 : invalid argument type'" **

Josh Kraushaar Over a year ago

I am using double exclamation marks, but weirdly the error only returns !index2 rather than !!index2

CPak Over a year ago

Looks like it's failing on tidyr::complete. You should ask a separate question to see if NSE evaluations are possible with tidyr::complete and tidyr::spread

Josh Kraushaar Over a year ago

It fails if I just use tidyr::select, and it fails before tidyr::spread is even processed (or if I comment tidyr::spread out and only test the first block of tidyr code)

Josh Kraushaar Over a year ago

It seems like it is processing !!index2 as !(!index2). Can I avoid that?

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