[R] Problem with Plotting in R

[rsherry8]

Please consider the following R statements:

     > x = seq(1:1632)
     > length( MyData$NWorth )
     [1] 1632
     > length( MyData$NWorthSm )
     [1] 1632
     > plot( x, MyData$NWorth, type="l" )
     > plot( x, MyData$NWorthSm, type="l" )
     > plot( x, MyData$NWorth, MyData$NWorthSm, type="l" )

All of the above statements work except for the last one. The last one 
produces the following message:

     Error in plot.window(...) : invalid 'xlim' value

So I then tired this:

     > xlim1 = c(0, 5000)
     >plot( x, MyData$NWorth, MyData$NWorthSm, type="l", xlim = xlim1 )

Which produced the following error message:
     Error in plot.window(...) : invalid 'ylim' value

So, I tired this:
     > ylim1 = c(0,9000)
     > plot( x, MyData$NWorth, MyData$NWorthSm, type="l", xlim = xlim1, 
ylim = ylim1 )

Which produced the following error message:
     Error in strsplit(log, NULL) : non-character argument

I would like to know what I am doing wrong.

Thank you,
Bob