[R] Plotting multiple columns on same graph

[Andrew Perrin]

I'd like to produce a series of simple line graphs for my methods class
that show the three questions used on a repeated survey to make up a
particular index.  The data frame is:

> efficacy.df
   year complicated havesay dontcare
1  1952          71      68       63
2  1954          NA      NA       NA
3  1956          64      71       71
4  1958          NA      NA       NA
5  1960          59      72       73
6  1962          NA      NA       NA
7  1964          67      70       62
8  1966          69      60       57
9  1968          71      58       55
10 1970          73      64       50
11 1972          74      59       49
12 1974          72      57       46
13 1976          70      56       44
14 1978          NA      53       45
15 1980          71      59       43
16 1982          NA      52       50
17 1984          70      68       57
18 1986          66      NA       43
19 1988          66      50       37
20 1990          65      34       23
21 1992          63      57       37
22 1994          73      34       22
23 1996          60      38       24
24 1998          71      46       25
25 2000          NA      50       33


The ideal graph will show each of the three questions as a different
color line, with lines connecting years spanned by NA values.  What's the
easiest way to do this?

Thanks.

----------------------------------------------------------------------
Andrew J Perrin - andrew_perrin at unc.edu - http://www.unc.edu/~aperrin
 Assistant Professor of Sociology, U of North Carolina, Chapel Hill
      269 Hamilton Hall, CB#3210, Chapel Hill, NC 27599-3210 USA


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