Question

what is "stem" used in Matlab program

Answer 1

A circle (the default) or other marker whose y-position represents the data value terminates each stem. stem(Y) plots the data sequence Y as stems that extend from equally spaced and automatically generated values along the x-axis. When Y is a matrix, stem plots all elements in a row against the same x value.

Answer 2

stem plots the data sequence Y as stems that extend from equally spaced and automatically generated values along X-axis.when Y is a matrix, stem plts all the elements in a row against the same X value.