The data file contains three variables: `trainx`, `trainy`, `testx`.

-  `trainx` is a 463715×90 matrix of training data, where each row is a 90-dimensional feature representation of a song.
- `trainy` is a 463715×1 vector of labels associated with each training data. Each row is the release year of the corresponding song in `trainx`.
- `testx` is a 51630×90 matrix of test data.

Special note for those who are not using Matlab: Python users can use scipy to read in the mat file, R users can use R.matlab package to read in the mat file.