polyFeatures.m

function [X_poly] = polyFeatures(X, p)
  %POLYFEATURES Maps X (1D vector) into the p-th power
  %   [X_poly] = POLYFEATURES(X, p) takes a data matrix X (size m x 1) and
  %   maps each example into its polynomial features where
  %   X_poly(i, :) = [X(i) X(i).^2 X(i).^3 ...  X(i).^p];
  %
  
  X_poly = X_poly = zeros(numel(X), p);
  X_poly(:, 1) = X;

  for degree = 2:p
      X_poly(:, degree) = X_poly(:, degree - 1) .* X;
  endfor
end