R help - Aug 2009 - How do I plot: regression line, regression line + s.d, regression line - s.d on the same chart?

Hello all,
I've got a scatter plot, for which I create a regression line using:
reg<- lm(yvars~xvars) and can plot the regression through the scatter
just fine.
I'd like to add two additional lines on the scatter plot: one being
regressionline+standard deviation, the other being
regressionline-standard deviation, thus creating some kind of 'band'
for the scatter.

Any help will be much appreciated. Thanking you in advance,

George.

have a look at predict.lm() and specifically at the 'interval' argument 
-- check also the following

x <- runif(100, -5, 5)
y <- 3 + 2 * x + rnorm(100, sd = 2)

fit <- lm(y ~ x)
xx <- seq(min(x), max(x), length.out = 30)
pred <- predict(fit, newdata = data.frame(x = xx), interval = "p")

plot(x, y)
matlines(xx, pred, lty = c(1, 2, 2), col = "red")


I hope it helps.

Best,
Dimitris


Jorgy Porgee wrote:
> Hello all,
> I've got a scatter plot, for which I create a regression line using:
> reg<- lm(yvars~xvars) and can plot the regression through the scatter
> just fine.
> I'd like to add two additional lines on the scatter plot: one being
> regressionline+standard deviation, the other being
> regressionline-standard deviation, thus creating some kind of
'band'
> for the scatter.
> 
> Any help will be much appreciated. Thanking you in advance,
> 
> George.
> 
> ______________________________________________
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> 
-- 
Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus University Medical Center

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