Removed unnecessary variables and renamed variables to appropriate name
Extract only 'year' from the release_date variable(originally "2019-06-14" or "2011" format) and then assign it to a new variable called "year"
Since release_date variable(originally "2019-06-14" or "2011" format) is non-consistent format, use if_else statement to make it consistent
The datatype of the year variable is chr so change the datatype to int

https://github.com/jaehee99/CSC_485_Music_Project/blob/main/data/Spotify_Music_Cleaning.R

https://github.com/jaehee99/CSC_485_Music_Project/blob/main/data/histogram_data.R

Group by genre and year, in order to find the mean values of the audio features. Use inner join to combine all of the datasets into one dataset. This is used for multiple line charts

https://github.com/jaehee99/CSC_485_Music_Project/blob/main/data/mean_value_music_data.R

Group by genre, subgenre, year in order to find the mean popularity value. This is for bubble chart

https://github.com/jaehee99/CSC_485_Music_Project/blob/main/data/subgenre_music.R