How would you extract the second column from my_matrix?

> my_matrix[ , 2]> my_matrix[2, 2]> my_matrix[2, ]

Fantastic! Using only the 1st index would extract an entire row, the 2nd index an entire column, and specifying both extracts a single element.

Yikes! Using only the 1st index would extract an entire row, the 2nd index an entire column, and specifying both extracts a single element.