stat_function conflict with loop in R

Question

I have a table called join_boin. and there is 4 column.

list <- c("a", "b", "c", "d)

function <- function(a){
  
  for (i in list){
    table %>%
      ggplot(aes(!!as.name(i)))+
      geom_histogram(aes(y=amount)) +
  stat_function(fun = dnorm, args = list(mean = mean(table$a), sd = sd(table$a)))  -> result
    
    print(result)
  }
}

When I use a loop to create a distribution for 4 variable's histograms, I don't know how to deal with (mean = mean(table $ DIFFERENT VARIABLES) ...

Answer 1

Instead of $, use [[. In the OP's code, the argument passed into function is av_total, whereas the for loop uses the list object created outside the function. It should be the same as av_total (or change the argument to 'av_total_list')

functiona <- function(data, av_total_list){  
   for(av_total in av_total_list) {
    data %>%
      ggplot(aes(!!as.name(av_total)))+
      geom_histogram(aes(y= ..density..), bins = 42) +
  stat_function(fun = dnorm, colour = "red", 
                args = list(mean = mean(data[[av_total]]),
             sd = sd(data[[av_total]])))  -> myresult
    
    print(myresult)
  }
}

and call it as

functiona(join_boston, list)

reproducible with

vec <- c('mpg', 'disp', 'hp')
functiona(mtcars, vec)

---

The above function just print the output into the console. Instead, it may be better to create a function that return the output and loop over the list and apply the function

library(dplyr)
library(ggplot2)
library(purrr)
functionb <- function(data, av_total) {
      data %>%
        ggplot(aes(.data[[av_total]])) + 
            geom_histogram(aes(y = ..density..), bins = 42) + 
            stat_function(fun = dnorm, colour = "red",
              args = list(mean = mean(data[[av_total]], na.rm = TRUE),
                        sd = sd(data[[av_total]], na.rm = TRUE)))
       }

and call the function by loop over the column names

out <- map(list, ~ functionb(join_boston, .x))

As a reproducible example for testing

data(mtcars)
library(ggpubr)
vec <- c('mpg', 'disp', 'hp')
out <- map(vec, ~ functionb(mtcars, .x))
ggarrange(plotlist = out, ncol = 2, nrow = 2)

-output