Creating multiple graphs based on one variable

Dear List,

I would like to create several graphs of similar data.  I have x and y values for several different individuals (in this case fish).  I would like to plot the x and y values for each fish separately.  I can do it using a for loop, but I think I should be using "apply".  Please let me know what I am doing wrong, or if there is a "better" way to do this.  What I have is:

#Test data
dat<-data.frame(c(rep(1:10,4)),c(rep(1:10,4)),c(rep(c("Tony","Mike","Vicky","Fred"),each=10)))
names(dat)<-c("x","y","Name") 

#Create function to plot x and y
myplot<-function() plot(dat$x,dat$y)

#Apply the function to each of the names
par(mfcol=c(2,2))   
apply(dat,2,myplot,by=dat$Name) #Does not work - tried various versions

I would like separate plots for Tony, Mike, and Vicky.  What is the best way to do this?  

Thank!

Tim


Tim Clark
Department of Zoology 
University of Hawaii

library(ggplot2) ;
## If you want all the curves to be on the same plotting grid ;

p <- ggplot(dat, aes(x=x,y=y, group=Name)) ;
p + geom_line(aes(colour=Name)) ; ## Only one curve will be visible 
since they are all superposed.

## If you want the curves to be on separate plotting grids ;

p <- ggplot(dat, aes(x=x,y=y, group=Name)) ;
p <- p + geom_line(aes(colour=Name)) ;
p+facet_grid(. ~ Name) ;