ggplot facet_wrap图

Question

my data set looks lik this:

x

date server cpu
1/1/2012 A  80
1/1/2012 B  20
1/1/2012 C  10
1/2/2012 A  80
1/2/2012 B  20
1/2/2012 C  10
1/3/2012 A  80
1/3/2012 B  20
1/3/2012 C  10
1/4/2012 A  80
1/4/2012 B  20
1/4/2012 C  10
1/5/2012 A  80
1/5/2012 B  20
1/5/2012 C  10
1/6/2012 A  80
1/6/2012 B  20
1/6/2012 C  10

I like to create a separate graph for each server using ggplot facet_wrap (unless there is a better way to do this?)

my code is this:

ggplot(x, aes(date, cpu, group=server, colour=server)) 
+ geom_point() 
+ facet_wrap(~server) 
+ ylim(0,100) 
+ theme_bw() 
+ geom_smooth(method="lm", se=TRUE, size=1) 
+ xlab("Date") 
+ ylab("CPU") 
+  opts(title="% CPU"),plot.title=theme_text(size=14, colour="navyblue"),axis.title.x = theme_text(face="bold", size=12, colour="#990000"), axis.text.x  = theme_text(angle=90, size=9, face="bold"),axis.title.y = theme_text(face="bold", size=12, colour="#990000", angle=90), axis.text.y=theme_text(size=9, face="bold", hjust=1)) + opts(legend.position = "none") 
+ opts(strip.text.x = theme_text(size=10, face="bold", colour="navyblue"), strip.background = theme_rect(colour="blue", fill="#98CAFF"))

This kinda works but I have two questions:

1. if the number of hosts is not evenly aligned, meaning sometimes, the last row may have less grids than previous rows due to number of hosts may be in odd number. So, last row grid graph have dates but the row before the last row does not have dates. How do I make sure that the row right before the last row has dates?
2. Since I will be scripting this, some data frames may have greater number of Servers. Depending on the number of of servers, I need to adjusted the png size. For example, if the number of Servers is 20, I need height of the image to be 500, width to be 200. Is there a way to do this in ggplot2? You probably have the idea. Other than ggplot2, is there any other way to do this?

Answer 1

In regard to question 2, you can use ggsave to save the last produced plot, some pseudocode which bases the plot width on the number of servers:

ggplot(...) + 
   etc()
if(noServers > 20) plot_width = 500
ggsave("name.png", width = plot_width)