plotting lm coeficients with their means

How about something like this?

my.func <- function(y, x1, x2, x3, x4  = NULL){
    my.formula <- as.formula("y ~ x1 + x2 + x3 + x4")
    if(is.null(x4)) { my.formula <- as.formula("y ~ x1 + x2 + x3") }
    outlm <- lm(my.formula)
    meanvec<-c(mean(x1),mean(x2),mean(x3))
    if(is.null(x4) == F) { meanvec<-c(mean(x1),mean(x2),mean(x3),mean(x4)) }
    mf <- data.frame(Impact = outlm$coef[-1], Performance = meanvec)
    plot((mf),xlab="Impact",ylab="Performance", type = "n")
    points(mf, pch=21, bg="grey", cex=4)
    text(x = mf$Impact, y = mf$Performance, labels = rownames(mf))
    abline(h=mean(mf$Performance))
    abline(v=mean(mf$Impact))
}

response <- 1:10
pred.1 <- rnorm(10)
pred.2 <- runif(10)
pred.3 <- pred.1 + runif(10)
pred.4 <- runif(10)
my.func(y = response, x1 = pred.1, x2 = pred.2, x3 = pred.3)
my.func(y = response, x1 = pred.1, x2 = pred.2, x3 = pred.3, x4 = pred.4)


You'd have to do some work to generalize it further. I don't have much
experience writing functions with missing args and I expect this is a dumb
way of doing it.

HTH, Andy

-----Original Message-----
From: r-help-bounces at stat.math.ethz.ch
[mailto:r-help-bounces at stat.math.ethz.ch]On Behalf Of Derek Margetts
Sent: Monday, November 08, 2004 11:39 AM
To: r-help at stat.math.ethz.ch
Subject: [R] plotting lm coeficients with their means


I am trying to write a function that will run a linear
model and plot the regression coeficients with their
corresponding means.  I am having two problems.  I can
get the plot with the function below, but I am having
trouble labeling the points.


function(y,x1,x2,x3,x4){
outlm<-lm(y~x1+x2+x3+x4)
imp<-as.data.frame(outlm$coef[-1])
meanvec<-c(mean(x1),mean(x2),mean(x3),mean(x4))
out<-list(imp,meanvec)
mf<-as.data.frame(out)
plot((mf),xlab="Impact",ylab="performance")
abline(h=mean(meanvec))
abline(v=mean(imp))
}

Problem #2:  If I only input x1,x2,and x3 how do I get
the function to ingnore the 4th instead of giving me
the unused argument error?

Thanks
Derek

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