Multi-class training data set.
zipcode
An object of class list of length 2.
https://web.stanford.edu/~hastie/ElemStatLearn/
https://www.csie.ntu.edu.tw/~cjlin/libsvmtools/datasets/regression.html
Normalized handwritten digits, automatically scanned from envelopes by the U.S. Postal Service. The original scanned digits are binary and of different sizes and orientations; the images here have been deslanted and size normalized, resulting in 16 x 16 grayscale images (Le Cun et al., 1990).