Write a reverse Polish notation calculator. In reverse Polish notation (also known as HP calculator notation), mathematical expressions are written with the operator following its operands. For example, 3 + 4 becomes 3 4 +. Order of operations is entirely based

Least square fit to polynomial write a function leastsquarefit3pol that solves a linear system of equations to find a least squares fit of a third order polynomial to an experimental data set given as two row arrays. the function leastsquarefit3pol must explicitly solve a set of linear equations and cannot use polyfit. there should be no restriction on the size of the problem that can be solved.