function pred = regress_pred(price, quantity, degree, prefunc)

	days = size(price, 1) - size(quantity, 1);
	product_count = size(price, 2);
	test_count = size(quantity, 1);
	test_set = 1:test_count;
	pred_set = test_count+1:size(price, 1);

	pred = zeros(days, product_count);
	for i = 1:product_count
		mn = regress(prefunc(price(test_set, i)), quantity(test_set, i), degree);
		pred(:, i) = polyval(mn, prefunc(price(pred_set, i)));
	end
	pred = max(pred, 0);

endfunction