# Thread: Is it linear regression ?

1. ## Is it linear regression ?

Hello ,

according to https://en.wikipedia.org/wiki/Polyno...on_and_example
the equation

is linear regression .

I want to know , is the equation Y=a1*x1^2+a2*x2^0.4 linear or not ? ( X1,X2 ) are independent variable

In general form : Y=a1*x1^b1+a2*x2^b2+......+an*xn^bn
Is non-linear ??????????
if ( b1, b2,b3,...,bn ) be anything except 1 ?

I want to use Non-linear regression analyse for estimate strength of concrete ..........

I have some data with 4 independent variable ( Xi) and one dependent variable concrete strength ( Yi ) ..........

I used this equation Y=a1*x1^b1+a2*x2^b2+a3*x3^b3+a4*x2^b4 and found Coefficients ( a1,a2 a3 a4 ) and ( b1,b2,b3,b4) By SPSS ..........

Is my equation wrong for Non-linear regression analyse ?

2. ## Re: Is it linear regression ?

I want to use Non-linear regression analyse for estimate strength of concrete ..........

I have some data with 4 independent variable ( Xi) and one dependent variable concrete strength ( Yi ) ..........

I used this equation Y=a1*x1^b1+a2*x2^b2+a3*x3^b3+a4*x2^b4 and found Coefficients ( a1,a2 a3 a4 ) and ( b1,b2,b3,b4) By SPSS ..........

Is my equation wrong for Non-linear regression analyse ?

3. ## Re: Is it linear regression ?

I think you are confusing linear regression, a general method, with whether a term is linear. You can use "linear regression" [the method] with non-linear terms for instance a quadratic or cubic term used to model time. Non-linear terms such as quadratics can be used in what is commonly called liner regression. I believe some call the use of non-linear terms in linear regression non-linear regression while some reserve that term for analysis such as splines or General Additive Model [which differs significantly from common linear regression].

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