Sorry about this. So, I have attempted to use reprex but because I am running R on a Linux server that isn't mine, I can't get the xclip to install and when I run reprex I get an error saying that X11 requires xclip, and I don't have access to install that.

```
No input provided and clipboard is not available.
Rendering reprex...
Clipboard on X11 requires 'xclip' (recommended) or 'xsel'.
Unable to put result on the clipboard'
```

For my original problem:

I have the following libraries installed:

```
library(tidyverse)
library(caret)
library(data.table)
library(lubridate)
library(knitr)
library(ggplot2)
```

The code I am running when I get the error is:

```
RMSE <- function(predicted_ratings, true_ratings){
sqrt(mean((predicted_ratings - true_ratings)^2))
}
# Calculated Predicted Ratings with Movie Effect
predicted_ratings <- mu + edx_test %>
left_join(movie_avgs, by='movieId') %>%
.$b_i
# Calculate Predicted Ratings with Movie Effect
predicted_ratings <- mu + edx_test %>%
left_join(movie_avgs, by='movieId') %>%
.$b_i
# Calculate RMSE for Movie Effect Term Plus Mean (Mu)
RMSE_2 <- RMSE(predicted_ratings, edx_test$rating, na.rm = TRUE)
```

The error I get from this code is:

```
Error in RMSE(predicted_ratings, edx_test$rating, na.rm = TRUE) :
unused argument (na.rm = TRUE)
```