Start a fresh of R session by launching RStudio. If RStudio is already open, you can start a fresh R session by going to menu item: Session > Restart R. Note in a fresh R session, there is no library loaded. So, if you execute the following, you will be given an error. df0 <- tibble(X = c("a","b","c"), Y = c(101,102,103), Z = c(10,20,30) Remember tibble function are from tibble library which comes with tidyverse. We often load tidyverse for convenience. If we do load tidyverse by calling library(tidyverse) Links to an external site. , it will load the core tidyverse packages.  However, we do not have to load a "mega" library like tidyverse if we are going to use only one or two functions from libraries included in tidyverse. Instead, you can load the specific library, whose function(s) you want to use. In the above case, you only need to load tibble library. library(tibble) df0 <- tibble(X = c("a","b","c"), Y = c(101,102,103), Z = c(10,20,30)) Since tibble is loaded,  df0 was successfully created. Now, you wanted to convert the data type of the Y column to character. Here is the code, part of which is redacted: library(XXX) df1 <- df0 %>%        mutate( XXX = XXX(Y)) Complete the code below so that df1 is successfully created. library( [ Select ] readr dplyr babynames sauder ) df1 <- df0 %>% mutate( [ Select ] X Y Z = [ Select ] is.character as.character is.numeric as.numeric (Y))