diff --git a/Statistics/LinearRegression.hs b/Statistics/LinearRegression.hs
--- a/Statistics/LinearRegression.hs
+++ b/Statistics/LinearRegression.hs
@@ -1,33 +1,64 @@
-module Statistics.LinearRegression (linearRegression) where
+{-# LANGUAGE BangPatterns #-}
 
+module Statistics.LinearRegression (linearRegression, correl, covar) where
+
 import qualified Data.Vector.Unboxed as U
-import Statistics.Sample
+import qualified Statistics.Sample as S
 
 --- * Simple linear regression
 
--- | Covariance
-covar :: Sample -> Sample -> (Double, Double, Double)
-covar xs ys = (U.sum (U.zipWith (*) (U.map f1 xs) (U.map f2 ys)) / (n-1), m1, m2)
+-- | Covariance of two samples
+covar :: S.Sample -> S.Sample -> Double
+covar xs ys = U.sum (U.zipWith (*) (U.map f1 xs) (U.map f2 ys)) / (n-1)
     where
-          n = fromIntegral $ U.length xs
-          m1 = mean xs
-          m2 = mean ys
+          !n = fromIntegral $ U.length xs
+          !m1 = S.mean xs
+          !m2 = S.mean ys
           f1 = \x -> (x - m1)
           f2 = \x -> (x - m2)
+{-# INLINE covar #-}
 
+
 -- | Pearson's product-moment correlation coefficient
-correl :: Sample -> Sample -> (Double, Double, Double, Double, Double)
-correl xs ys = let (c, m1, m2) = covar xs ys
-                   sx = stdDev xs
-                   sy = stdDev ys
-               in (c / (stdDev xs * stdDev ys), m1, m2, sx, sy)
+correl :: S.Sample -> S.Sample -> Double
+correl xs ys = let !c = covar xs ys
+                   !sx = S.stdDev xs
+                   !sy = S.stdDev ys
+               in c / (sx * sy)
+{-# INLINE correl #-}
 
 -- | Simple linear regression between 2 samples.
 --   Takes two vectors Y={yi} and X={xi} and returns
---   (alpha, beta) such that Y = alpha + betaX
-linearRegression :: Sample -> Sample -> (Double, Double)
+--   (alpha, beta, r*r) such that Y = alpha + beta*X
+--   and where r is the Pearson product-moment correlation
+--   coefficient
+linearRegressionRSqr :: S.Sample -> S.Sample -> (Double, Double, Double)
+linearRegressionRSqr xs ys = (alpha, beta, r*r)
+    where 
+          !c                   = U.sum (U.zipWith (*) (U.map (subtract m1) xs) (U.map (subtract m2) ys)) / (n-1)
+          !r                   = c / (sx * sy)
+          !m1                  = S.mean xs 
+          !m2                  = S.mean ys
+          !sx                  = S.stdDev xs
+          !sy                  = S.stdDev ys
+          !n                   = fromIntegral $ U.length xs
+          !beta                = r * sy / sx
+          !alpha               = m2 - beta * m1
+{-# INLINE linearRegressionRSqr #-}
+          
+-- | Simple linear regression between 2 samples.
+--   Takes two vectors Y={yi} and X={xi} and returns
+--   (alpha, beta, r*r) such that Y = alpha + beta*X          
+linearRegression :: S.Sample -> S.Sample -> (Double, Double)
 linearRegression xs ys = (alpha, beta)
     where 
-          (r, m1, m2, sx, sy) = correl xs ys
-          beta                = r * sy / sx
-          alpha               = m2 - beta * m1
+          !c                   = U.sum (U.zipWith (*) (U.map (subtract m1) xs) (U.map (subtract m2) ys)) / (n-1)
+          !r                   = c / (sx * sy)
+          !m1                  = S.mean xs 
+          !m2                  = S.mean ys
+          !sx                  = S.stdDev xs
+          !sy                  = S.stdDev ys
+          !n                   = fromIntegral $ U.length xs
+          !beta                = r * sy / sx
+          !alpha               = m2 - beta * m1
+{-# INLINE linearRegression #-}
diff --git a/statistics-linreg.cabal b/statistics-linreg.cabal
--- a/statistics-linreg.cabal
+++ b/statistics-linreg.cabal
@@ -7,7 +7,7 @@
 -- The package version. See the Haskell package versioning policy
 -- (http://www.haskell.org/haskellwiki/Package_versioning_policy) for
 -- standards guiding when and how versions should be incremented.
-Version:             0.1
+Version:             0.2
 
 -- A short (one-line) description of the package.
 Synopsis:            Linear regression between two samples, based on the 'statistics' package
@@ -16,7 +16,7 @@
 Description:         Provides a function to perform a linear regression between 2 samples, see the documentation of the linearRegression function. This library is based on the 'statistics' package.
 
 -- URL for the project homepage or repository.
-Homepage:            http://code.haskell.org/~alpmestan/linreg/
+Homepage:            http://github.com/alpmestan/statistics-linreg
 -- The license under which the package is released.
 License:             MIT
 
@@ -31,7 +31,7 @@
 Maintainer:          Alp Mestanogullari <alpmestan@gmail.com>
 
 -- A copyright notice.
-Copyright:           2010 Alp Mestanogullari
+Copyright:           2010-2011 Alp Mestanogullari
 
 -- Stability of the pakcage (experimental, provisional, stable...)
 Stability:           Experimental
@@ -54,7 +54,8 @@
   
   -- Packages needed in order to build this package.
   Build-depends: statistics >= 0.5, vector >= 0.5, base >= 4 && < 5
-  
+
+  Ghc-options: -funbox-strict-fields  
   -- Modules not exported by this package.
   -- Other-modules: