From c44e670ebbb1e1690398ac2837e5e79e17a19c7b Mon Sep 17 00:00:00 2001
From: Benjamin Franzke <benjaminfranzke@googlemail.com>
Date: Sat, 12 May 2012 15:04:03 +0200
Subject: Use polyval where appropriate

..instead of doing the polynom multiplication by hand.
---
 log_regress_pred.m  | 11 ++---------
 quad_regress_pred.m |  9 +++------
 regress.m           |  4 +---
 regress_pred.m      |  4 ++--
 4 files changed, 8 insertions(+), 20 deletions(-)

diff --git a/log_regress_pred.m b/log_regress_pred.m
index 3c90441..e6cfe05 100644
--- a/log_regress_pred.m
+++ b/log_regress_pred.m
@@ -8,15 +8,8 @@ function pred = log_regress_pred(price, quantity)
 
 	pred = zeros(days, product_count);
 	for i = 1:product_count
-		[a,b] = regress_log(price(test_set, i), quantity(test_set, i));
-		pred(:, i) = a * log(price(pred_set, i)) + b;
+		ab = regress(log(price(test_set, i)), quantity(test_set, i));
+		pred(:, i) = polyval(ab, log(price(pred_set, i)));
 	end
 
 endfunction
-
-
-function [a,b] = regress_log(x, y)
-	ab = [ log(x) ones(length(x), 1) ] \ y;
-	a = ab(1);
-	b = ab(2);;
-endfunction
diff --git a/quad_regress_pred.m b/quad_regress_pred.m
index aef8822..d9e3b6e 100644
--- a/quad_regress_pred.m
+++ b/quad_regress_pred.m
@@ -8,16 +8,13 @@ function pred = quad_regress_pred(price, quantity)
 
 	pred = zeros(days, product_count);
 	for i = 1:product_count
-		[a,b,c] = regress2(price(test_set, i), quantity(test_set, i));
-		pred(:, i) = a .* price(pred_set, i).^2 + b * price(pred_set, i) + c;
+		abc = regress2(price(test_set, i), quantity(test_set, i));
+		pred(:, i) = polyval(abc, price(pred_set, i));
 	end
 
 endfunction
 
 
-function [a,b,c] = regress2(x, y)
+function abc = regress2(x, y)
 	abc = [ x.^2 x ones(length(x), 1) ] \ y;
-	a = abc(1);
-	b = abc(2);
-	c = abc(3);
 endfunction
diff --git a/regress.m b/regress.m
index 5a7336b..ad06796 100644
--- a/regress.m
+++ b/regress.m
@@ -1,6 +1,4 @@
-function [m, n] = regress(x, y)
+function mn = regress(x, y)
   mn = [ x ones(length(x), 1) ] \ y;
-  m = mn(1);
-  n = mn(2);
 endfunction
 
diff --git a/regress_pred.m b/regress_pred.m
index 0c66b1e..2992471 100644
--- a/regress_pred.m
+++ b/regress_pred.m
@@ -8,8 +8,8 @@ function pred = regress_pred(price, quantity)
 
 	pred = zeros(days, product_count);
 	for i = 1:product_count
-		[m,n] = regress(price(test_set, i), quantity(test_set, i));
-		pred(:, i) = m .* price(pred_set, i) + n;
+		mn = regress(price(test_set, i), quantity(test_set, i));
+		pred(:, i) = polyval(mn, price(pred_set, i));
 	end
 
 endfunction
-- 
cgit