[R] Question on partial effect

[Gavin Simpson]

On Tue, 2006-07-11 at 23:51 +0800, Guo Wei-Wei wrote:
> Dear all,
> 
> I don't know what's my question is called. I have a performance
> variable A, such as sales. And I have another variable B, let's say
> establish time of firm. I want to create the third variable that is
> sales without the effect of establish time. Maybe it can be called
> partial effect problem. I'm not sure.
> 
> Does anyone have any suggestion? Thank you in advance!
> 
> All the best,
> Wei-Wei

Do you mean?

## dummy data
A <- rnorm(100)
B <- rnorm(100)
C <- resid(lm(A ~ B))

C now contains the residual variation in A after fitting B.

e.g. with some real data
?cars
data(cars) # not sure this is needed now, I forget
mod <- lm(dist ~ speed, data  = cars)
summary(mod)
partial <- resid(mod)

## check
mod2 <- lm(dist ~ partial, data = cars)
summary(mod2)
## from the two R^2 form mod1 and mod2 - partial contains dist minus
## the effects of speed
> 0.6511 + 0.3489
[1] 1

HTH

G
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