How to plot a vector function in 3d
I would like to plot the following vector function: ||Xa-b||^2_2 for a 2D vector a. This should result in a 3d surface plot, where the "x" axis is a1, and "y"-axis is a2.
Note this is a real valued function, whose input is a vector. I can also write it out as a function of a1 and a2 but if it all possible I would rather not! I want to use this in a linear algebra class and I want the formula we plot to maintain the semi-confusing (to the students) linear algebraic notation as much as possible.