rename columns based on a variable in r

my_data %>% 
  rename(
    sepal_length = Sepal.Length,
    sepal_width = Sepal.Width
    )

# df = dataframe
# old.var.name = The name you don't like anymore
# new.var.name = The name you want to get

names(df)[names(df) == 'old.var.name'] <- 'new.var.name'

df <- rename(df, new_name = old_name) #For renaming dataframe column
 
tbl <- rename(tbl, new_name = old_name) #For renaming tibble column
 
tbl <- tbl %>% rename(new_name = old_name) #For renaming tibble column using dplyrpipe 
                                           #operator