[R] Creating a simple function

[Zachary Lim]

Hi,

I'm trying to create a simple function that takes a dataframe as its only argument. I've been using gmodels::CrossTable, but it requires a lot of arguments, e.g.:

#this runs fine
CrossTable(data$col1, data$col2, prop.chisq = FALSE, prop.c = FALSE, prop.t = FALSE, format = "SPSS")

Moreover, I wanted to make it compatible with piping, so I decided to create the following function:

ctab <- function(data) {
  CrossTable(data[,1], data[,2], prop.chisq = FALSE, prop.c = FALSE, prop.t = FALSE, format = "SPSS")
}

When I try to use this function, however, I get the following error:

#this results in 'Error: Must use a vector in `[`, not an object of class matrix.'
data %>% select(col1, col2) %>% ctab()

I tried searching online but couldn't find much about that error (except for in specific and unrelated cases). Moreover, when I created a very simple dataset, it turns out there's no problem:

#this runs fine
data.frame(C1 = c('x','y','x','y'), C2 = c('a','a','b','b')) %>% ctab()


Is this a problem with my function or the data? If it's the data, why does directly calling CrossTable work?

Thanks!

Best,
Zach

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