How to use arguments as character in a function?

General
2

Hi, and welcome!

Please see the FAQ: What's a reproducible example (`reprex`) and how do I do one? Using a reprex, complete with representative data will attract quicker and more answers. You've done a good job here, just missing a bit.

The most pressing issue is the y argument to SummarizeFn, Price. It's not in the namespace because it's embedded in df.

The simplest fix to that part of the problem is using df$price as the y argument

suppressPackageStartupMessages(library(dplyr))
df <- data.frame("Treatment" = c(rep("A", 2), rep("B", 2)), "Price" = 1:4, "Cost" = 2:5)
SummarizeFn <- function(x,y) {
  x %>% group_by(Treatment) %>% 
    summarize(
      n = n(),
      Mean = mean(y), 
      SD = sd(y)
    ) %>% cbind ("Var" = rep(y, 3)) # add a column to show which variable those statistics belong to. 
}
SumPrice <- SummarizeFn(df, df$Price)
SumPrice
#>    Treatment n Mean       SD Var
#> 1          A 2  2.5 1.290994   1
#> 2          B 2  2.5 1.290994   2
#> 3          A 2  2.5 1.290994   3
#> 4          B 2  2.5 1.290994   4
#> 5          A 2  2.5 1.290994   1
#> 6          B 2  2.5 1.290994   2
#> 7          A 2  2.5 1.290994   3
#> 8          B 2  2.5 1.290994   4
#> 9          A 2  2.5 1.290994   1
#> 10         B 2  2.5 1.290994   2
#> 11         A 2  2.5 1.290994   3
#> 12         B 2  2.5 1.290994   4

Created on 2020-03-30 by the reprex package (v0.3.0)