[R] Polynomial regression problem
Matthew McKinney
mm.entomology at gmail.com
Tue Mar 15 15:41:12 CET 2011
I have just started using R so forgive me if this question is very
simple. I have a data set (in a data frame called dm) that looks like
this
x (Cells) y(males)
1 0
2 2
3 7
4 12
5 12
6 19
7 22
8 23
9 25
10 23
11 23
12 11
13 8
14 3
15 0
16 0
I centered the dependent and predictor variables and then squared the
predictor to make a quadratic variable.
This left me with 3 variables:
MalesC
CellsC
CellsC2
I then used: >quadraticModel <- lm(MalesC ~ CellsC + CellsC2, data = dm)
This has given me R^2= 0.8821, F= 48.63, and p<0.001
I ran the exact same data in sigma plot and got identical results. My
problem comes from the estimated coefficients I am getting in R when
using >summary(quadraticModel). My coefficient estimates in sigma plot
fit my data set well and agree with Microsoft excels estimates. The
results from R appear to be the coefficients of a curve fitting the
residuals. If I >plot(quadraticModel) it does not draw a curve fitting
my data, but rather the residuals.
What I would like to know is how I can get the coefficient estimates
for the data rather than the residuals, and how to plot that in R.
Thanks,
Matthew McKinney
More information about the R-help
mailing list