/************************************************/
/* This data set examines number of foggy days  */
/* annually from 1948 to 2003.  The years 1963  */
/* to 1998 are missing.  Station 13741 is       */
/* located in Roanoke VA                        */
/************************************************/

data agency13741;
input Year Days;  * Number of foggy days;
/* Recording method changed in 1980     */
if year < 1980 then PrePost=1; else PrePost=2;
datalines;
1948 45.24
1949 49
1950 37
1951 28
1952 22
1953 21
1954 18
1955 23
1956 27
1957 42
1958 24
1959 27
1960 23
1961 21
1962 24
1963 .
1964 .
1965 .
1966 .
1967 .
1968 .
1969 .
1970 .
1971 .
1972 .
1973 .
1974 .
1975 .
1976 .
1977 .
1978 .
1979 .
1980 .
1981 .
1982 .
1983 .
1984 .
1985 .
1986 .
1987 .
1988 .
1989 18
1990 10
1991 8
1992 18
1993 11
1994 5
1995 13
1996 31
1997 21
1998 16
1999 9.02
2000 17
2001 12
2002 8
2003 13
title "Times Series for Station 13741";
proc gplot;
symbol1 v=dot i=join;
symbol2 v=none i=r;
plot days*year=1 days*year=2/overlay;
run;
proc sort; by prepost;
proc autoreg;
model days=year/dwprob;
run;
proc autoreg; by prepost;
model days=year/dwprob;
run;
proc autoreg;
model days=year/nlag=2 method=ml;
run;