How to create a function with "not equal to"?

Question

I have a function that I'm trying to create using filter !=, but it doesn't work. I wonder if it is due to something related with tidy evaluation.

This is what I tried:

library(haven)
library(dplyr)
library(labelled)
library(sjlabelled)

data <- read_spss("http://staff.bath.ac.uk/pssiw/stats2/SAQ.sav")
data$Q01_L <- as_label(data$Q01)

This is the function I tried to write:

    bar_plot <- function(data, var) {
      var <- rlang::ensym(var)
      
      data %>% 
        filter(!var == "Neither") %>% 
        ggplot(aes(!!var)) +
        geom_bar() +
        coord_flip() +
        theme_classic() +
        labs(x = "Question", y = "Count", title = var_label(data$var)) 
    }
    
    
    bar_plot(data, Q01_L)

What I am trying to achieve is to remove "Neither" values and I tried this using filter(!var == "Neither") but that doesn't work and I'm still getting "Neither" plotted. And I also lost the title of the chart.

This is what I'm trying to achieve:

I was able to do this with a few lines of code:

data %>% 
  filter(!Q01_L == "Neither") %>% 
  ggplot(aes(Q01_L)) +
  geom_bar() +
  coord_flip() +
  theme_classic() +
  labs(x = "Question", y = "Count", title = var_label(data$Q01_L)) 

But I'm not able to figure out how to convert it into a function.

Answer 1

You can use the curly-curly operator in a function, so that var <- rlang::ensym(var) can be removed.

From help("nse-force"):

The curly-curly operator {{ }} for function arguments is a bit special because it forces the function argument and immediately defuses it. The defused expression is substituted in place, ready to be evaluated in another context, such as the data frame.

bar_plot <- function(data, var) {
  
  data %>% 
    filter({{var}} != "Neither") %>% 
    ggplot(aes( {{var}} )) +
    geom_bar() +
    coord_flip() +
    theme_classic() +
    labs(x = "Question", y = "Count", title = var_label(pull(data, {{var}})))
}

bar_plot(data, Q01_L)