Martin Maechler wrote:
Yes, I think all your propositions would be improvements.
OTOH, I don't think the improvements warrant a big increase in
code (complexity), nor do I think the improvements are crucial
for R's integrity.
So...
If you (our someone else) provides a patch {against
R-devel, as always} which keeps the code simple,
I'd strongly consider adding that to R.
Dear Martin,
Thank you for the encouragement.
Please find a patch in attachment.
As you will see, I also added a warning
for models with more than 2 parameters.
Kind regards,
Tobias
Regards,
Martin Maechler
"Tobias" == Tobias Verbeke <[EMAIL PROTECTED]>
on Sat, 09 Dec 2006 22:42:38 +0100 writes:
Tobias> The abline function can be used to draw the
Tobias> regression line when one passes the lm object as an
Tobias> argument.
Tobias> However, if it's an intercept-only model, it appears
Tobias> to use the intercept as the slope of the abline:
Tobias> mod <- lm(dist ~ 1, data = cars) plot(dist ~ speed,
Tobias> data = cars) abline(reg = mod) # nothing appears
Tobias> This behaves as documented, but might catch
Tobias> someone. Would it be an improvement if this
Tobias> situation was detected so as to plot the appropriate
Tobias> horizontal line, i.e.
Tobias> abline(a = coef(mod), b = 0) ?
Tobias> Would it also be an improvement if for a model like
Tobias> mod2 <- lm(dist ~ 1 + offset(speed), data = cars)
Tobias> abline(reg = mod2) would be equivalent to
Tobias> abline(a = coef(mod2), b = 1) ?
Tobias> For models through the origin, the current function
Tobias> works fine, but one might even consider models
Tobias> through the origin and having the independent
Tobias> variable in an offset() to be fully fool-proof, i.e.
Tobias> abline(a = 0, b = 1)
Tobias> Kind regards, Tobias
Tobias> ______________________________________________
Tobias> R-devel@r-project.org mailing list
Tobias> https://stat.ethz.ch/mailman/listinfo/r-devel
11,12c11,15
< temp <- as.vector(coef(a))
< if(length(temp) == 1) {
---
> tempa <- as.character(terms(a))
> coefa <- coef(a)
> if (length(coefa) > 2)
> warning("The abline function is meant to only plot the regression
> line for simple linear regression")
> if (length(grep("-[[:blank:]]?1", tempa))) {
14c17
< b <- temp
---
> b <- ifelse(length(grep("offset", tempa)), 1, coefa[1])
16,17c19,22
< a <- temp[1]
< b <- temp[2]
---
> a <- coefa[1]
> if (length(grep("offset", tempa))) b <- 1
> else if (length(coefa) >= 2) b <- coefa[2]
> else b <- 0
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