On Apr 21, 2009, at 12:37 PM, Vemuri, Aparna wrote:
These are all field measured values.
For a little background here, I have field measurements of SO4, NO3
and NH4. I used these variables in an atmospheric chemistry model to
calculate PBW on a line-by-line basis.
To bypass the use of the complex atmospheric chemistry model in the
future, I want to develop a regression equation based on the current
results I have. Also, I know the atmospheric chemistry model
requires SO4, NO3 and NH4 to estimate PBW. So I am using the same as
IVs for the regression model.
Aparna
One way to create collinearity is to construct a new variable, say
PBW?, as a linear combination of the measurements. If you then re-
analyze that augmented dataset, you will naturally get the sort of
complaints or unexpected behavior from the R interpreter that you are
seeing.
--
David Winsemius
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