regression coeffiecients

I’m having troubles understand something about regression coefficients.
If I have two vectors:

x = [1.38, 1.98, 3.18, 3.56, 4.9, 6.21, 6.44, 7.47, 8.36, 8.81]
y = [8.19, 17.77, 20.12, 14.55, 20.17 ,31.22 ,28.94, 34.79, 40.26, 38.99]

and I would like to find out the regression coefficient I can use polyfit:

b1, b = polyfit(x,y,1)

my first question is can I get from polyfit the corrlation coeficient (I know about corrcoef, just looking for more opotions).

The second question is about a fuction I wrote: according to
it’s pretty easy to write a little python funcion to calculate the regression coefficients. Here is mine:

def b1(x,y):
sum1 = 0
sum2 = 0
mx = mean(x)
my = mean(y)
for i,j in zip(x,y):
sum1 =+ (i-mx)*(j-my)
print sum1
sum2 =+ (i-mx)**2
b1 = sum1/sum2

return b1

both methods yeild two different b1 values. Can anyone please tell me what wrong with my function ?

Thanks, Oz.


: :’ : We are Lower your prices,

.’ surrender your code.
`- We will add your hardware and software
distinctiveness to our own.
Resistance is futile.

        Imagine there's no countries

        It isn't hard to do
        Nothing to kill or die for
        And no religion too
        Imagine all the people
        Living life in peace

       You all must read 'The God Delusion'


when one person suffers from a delusion it is called insanity. When many people suffer from a delusion it is called religion."

Robert Pirsig, Zen and the Art of Motorcycle Maintenance