Pass formula to function in R?
formula, function, r, survey
Solution
You can use `reformulate` to construct your formula and call `svymean` within your function. Use `...` to pass `na.rm` or other arguments to `svymean`
stats <- function(terms, data, num, ...) {
.formula <- reformulate(terms)
repstat <- svymean(.formula, data, ...)
estmean <- as.numeric(round(100 * repstat[num], digits=0))
estse <- round(100 * sqrt(attributes(repstat)$var[num,num]), digits=1)
return(list(mean=estmean, se=estse))
}
stats(data = FraSvy, terms = "hq_ehla", 1, na.rm = TRUE)$mean
Have a look at this answer for more details on programmitically create formula objects
Or, you could pass a formula object within the function.
stats2 <- function(formula, data, num, ...) {
repstat <- svymean(formula, data, ...)
estmean <- as.numeric(round(100 * repstat[num], digits=0))
estse <- round(100 * sqrt(attributes(repstat)$var[num,num]), digits=1)
return(list(mean=estmean, se=estse))
}
stats2(data = FraSvy, formula = ~hq_ehla, 1, na.rm = TRUE)$mean
Problem
Any help with this would be really appreciated. I am using the Lumley survey package and am trying to simplify my code, but have hit a slight snag. The svymean function from the package is called as follows in my code, where the first argument is a formula indicating which variables I want, and the second argument is that dataset: ``` svymean(~hq_ehla, FraSvy, na.rm=TRUE) ``` I'm trying to create a function that will pull out the mean (proportions) and standard errors for categorical variables, so I've made the following function: ``` stats <- function(repstat, num) { estmean <- as.numeric(round(100 * repstat[num], digits=0)) estse <- round(100 * sqrt(attributes(repstat)$var[num,num]), digits=1) return(list(mean=estmean, se=estse)) } ``` This works, so when I'm pulling out the mean and se of my first category, for example, I use: ``` stats(svymean(~hq_ehla, FraSvy, na.rm=TRUE), 1)$mean stats(svymean(~hq_ehla, FraSvy, na.rm=TRUE), 1)$se ``` What I'd like to be able to do is simplify this to something much shorter, where maybe I'd only have to write: ``` stats(FraSvy, "hq_ehla", 1)$mean ``` Or something like that. Problem is that I can't figure out how to pass a formula to a function using a variable name.