[R] Trouble plotting with factor

[Paul Johnson]

With R 1.8.1 running in Fedora Core 1 Linux, I am having some trouble 
recoding and ploting some factor variables. 

First, can I give you some example data?
Here is a column of names for age groups:

agegroups <- c(   "15-19", "20-24", "25-29","30-34", "35-39", 
"40-44","45-49","50-54","55-59","60-64",  "65-69", "70-74", "75-79",  
"80-84", "OVER")

Here is an index for driver's license ownership in each age group:

  fracld            
0.4914204
0.9752746
1.0864465
1.0555984
1.0631969
1.0738725
1.0971969
1.0657212
1.0217373
0.9761226
0.9043233
0.9045744
0.8573243
0.7889182
0.5217992

I want to take several similar columns of numbers and put them into a 
single line plot, one line for each column. 

I can get a graph with the inside part that looks roughly like I want if 
I just do:

plot(fracld,type="l")

The horizontal axis, of course, is just the sequence from 1:15, not the 
age labels. That's no good.

But, If I try

plot(as.factor(agegroup), fracld, type="l")

the plot does not have the line I want, but rather only flat "steps" 
showing the values.  It does  have a nice looking horizontal axis, 
though, showing the age groups.

So I think to myself "I'll outsmart them by adding the lines after 
creating the plot", but if I do this

plot(agegroup,fracld,type="n")

The step markers still appear. 

So if I want the tick marks and value lables on the horzontal axis, 
there is apparently  no way to plot lines?

What to do?