library(datasets)
t.v<-c(1:72)
C1<-cos(2*pi*t.v/12); S1<-sin(2*pi*t.v/12)
C2<-cos(2*pi*t.v/6); S2<-sin(2*pi*t.v/6)
USA.ACC<-data.frame(as.numeric(USAccDeaths),S1,C1,S2,C2)
USA.ACC.fit<-lm(USAccDeaths~S1+C1+S2+C2,
                data=USA.ACC)$fitted
USA.ACC.coeff<-lm(USAccDeaths~S1+C1+S2+C2,
                data=USA.ACC)$coeff
t.c<-seq(from=1,to=72,by=0.01)
C1.c<-cos(2*pi*t.c/12); S1.c<-sin(2*pi*t.c/12)
C2.c<-cos(2*pi*t.c/6); S2.c<-sin(2*pi*t.c/6)

y.c<-USA.ACC.coeff[1]+USA.ACC.coeff[2]*S1.c+
     USA.ACC.coeff[3]*C1.c +USA.ACC.coeff[4]*S2.c+
     USA.ACC.coeff[5]*C2.c