Hello,
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 http://en.wikipedia.org/wiki/Regression_analysis#Linear_regression
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.
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