[R] plot with a regression line(s)

[R. Michael Weylandt <michael.weylandt@gmail.com>]

I'm not sure what your definition of easier would be, but there are some style things you might want to be aware of:

I) the name is likely to hit up against the S3 generic plot() when applied to a glm object. This might lead to strange bugs at some point. 
II) you can test !is.null once and use on.exit() to delay the clean-up call to dev.off()
III) I'm not sure about glm objects but abline() applied to an lm object automatically plots a best fit line saving you a line or so of code. 
IV) You probably don't want to print() m at the end: the REPL will print it automatically in interactive top level calls and it will be rather noisy if you start wrapping this in other calls. 

Hope this helps,
Michael

On Apr 4, 2012, at 11:13 AM, Sam Steingold <sds at gnu.org> wrote:

> I am sure a common need is to plot a scatterplot with some fitted
> line(s) and maybe save to a file.
> I have this:
> 
> plot.glm <- function (x, y, file = NULL, xlab = deparse(substitute(x)),
>                      ylab = deparse(substitute(y)), main = NULL) {
>  m <- glm(y ~ x)
>  if (!is.null(file))
>    pdf(file = file)
>  plot(x, y, xlab = xlab, ylab = ylab, main = main)
>  lines(x, y = m$fitted.values, col = "green")
>  if (!is.null(file))
>    dev.off()
>  print(m)
> }
> 
> is there a better/easier/more general way?
> 
> -- 
> Sam Steingold (http://sds.podval.org/) on Ubuntu 11.10 (oneiric) X 11.0.11004000
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