[R] plotting average effects.

[poliscigradstudent]

hi...  i am a phd student using r.  i am having difficulty plotting average
effects.  admittedly, i am not really understanding what each of the
commands mean so when i get the error i am not sure where the issue is.

here is my code...  i will include the points at which there are errors....

> dat2 <- dat3 <- dat
> dat2$popc100 <- dat2$popc100 + 1000
> dat2$popc100[which(dat2$popc100 > max(dat$popc100))] <- max(dat$popc100)
> dat3$popc100 <- dat$popc100 - 1000
> dat3$popc100[which(dat3$popc100 < min(dat$popc100))] <- min(dat$popc100)
> pred1 <- predict(mod, type="response")
> pred2 <- predict(mod, newdata=dat2, type="response")
> pred3 <- predict(mod, newdata=dat3, type="response")
> pop.group <- cut(dat$popc100kpc, breaks=quantile(dat$popc100kpc,
> seq(0,1,by=.3)), include.lowest=T)
> means <- by(cbind(pred1, pred2, pred3), list(pop.group), apply, 2, mean)
> means <- do.call(rbind, means)


> par(mar=c(7,4,4,2))
> plot(c(1,10), range(c(means)), type="n", xlab="", 
+ 	ylab="Predicted Probability", axes=F)
> plot(c(1,10), range(c(means)), type="n", xlab="pop pc by 100k", 
+ 	ylab="Predicted Probability", axes=F)
> arrows(1:10, means[,1], 1:10, means[,2], code=2, length=.1)
> arrows(1:10, means[,1], 1:10, means[,3], code=2, length=.1, col="red")
> points(1:10, means[,1], pch=16)
Error in xy.coords(x, y) : 'x' and 'y' lengths differ


as i understand it, i need to change the means[,1]....  i have tried a few
combos and i am not getting anywhere...  

further, my arrows are huge and points are not appearing in my plot.

is there anywhere i can find a break down of each of these commands and what
each part means?  i understand the lengths, colors, xlab, ylab, etc etc.

thanks in advance for any insight you can give me.


http://r.789695.n4.nabble.com/file/n3923982/effplot_copy.jpg 

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