Quote:
Originally Posted by gaurav.jain@umassmed.edu
hi everyone,
Can anyone please explain me how to transform the data using the nonlinear transformation is given by
phi(x1, x2) = (1, x1, x2, x21, x22 , x1x2, x1 − x2, x1 + x2)
I am just confused how to use that in my code. I mean for the new values which function to use for transformation?
is it x1=x1^2 and x2=x^2 and so on or something else. I am sure i am missing a big concept here. Any help would be great.
Thanks in advance.

There is a typo in the way you have written the vector above. The 4th term is x1^2, the fifth term is x2^2.
But basically you have the right idea. You are given a data vector with two values. Create a larger data vector of 8 terms, seven of which are dependent on the original two values you are given.
In the new vector the first three terms are 1, x1, x2. The remaining 5 terms are obtained by applying "transformations" to x1 and x2. For example, the sixth term is x1*x2.
Then you do linear regression on the new x matrix you have built which is (for the given in.data) an 8x35 matrix. 35 data vectors, each with 8 terms as above.