plot with a regression line(s)

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
http://www.childpsy.net/ http://truepeace.org http://openvotingconsortium.org
http://jihadwatch.org http://iris.org.il http://honestreporting.com
Even Windows doesn't suck, when you use Common Lisp

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?

-- 

-----Original Message-----
From: r-help-bounces at r-project.org 
[mailto:r-help-bounces at r-project.org] On Behalf Of Sam Steingold

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?