下面是本人自己写的程序，不知道如何写会更简单明了一些d44month<-matrix(0,ncol=58,nrow=44*12)
for(y in 1966:2009){
d44month[(y-1966)*12+1,4:58]<-sapply(d4465day[d4465day$YEAR==y&d4465day$MONTH==1,4:58],sum);d44month[(y-1966)*12+1,1:3]<-c(y,1,NA)
d44month[(y-1966)*12+2,4:58]<-sapply(d4465day[d4465day$YEAR==y&d4465day$MONTH==2,4:58],sum);d44month[(y-1966)*12+2,1:3]<-c(y,2,NA)
d44month[(y-1966)*12+3,4:58]<-sapply(d4465day[d4465day$YEAR==y&d4465day$MONTH==3,4:58],sum);d44month[(y-1966)*12+3,1:3]<-c(y,3,NA)
d44month[(y-1966)*12+4,4:58]<-sapply(d4465day[d4465day$YEAR==y&d4465day$MONTH==4,4:58],sum);d44month[(y-1966)*12+4,1:3]<-c(y,4,NA)
d44month[(y-1966)*12+5,4:58]<-sapply(d4465day[d4465day$YEAR==y&d4465day$MONTH==5,4:58],sum);d44month[(y-1966)*12+5,1:3]<-c(y,5,NA)
d44month[(y-1966)*12+6,4:58]<-sapply(d4465day[d4465day$YEAR==y&d4465day$MONTH==6,4:58],sum);d44month[(y-1966)*12+6,1:3]<-c(y,6,NA)
d44month[(y-1966)*12+7,4:58]<-sapply(d4465day[d4465day$YEAR==y&d4465day$MONTH==7,4:58],sum);d44month[(y-1966)*12+7,1:3]<-c(y,7,NA)
d44month[(y-1966)*12+8,4:58]<-sapply(d4465day[d4465day$YEAR==y&d4465day$MONTH==8,4:58],sum);d44month[(y-1966)*12+8,1:3]<-c(y,8,NA)
d44month[(y-1966)*12+9,4:58]<-sapply(d4465day[d4465day$YEAR==y&d4465day$MONTH==9,4:58],sum);d44month[(y-1966)*12+9,1:3]<-c(y,9,NA)
d44month[(y-1966)*12+10,4:58]<-sapply(d4465day[d4465day$YEAR==y&d4465day$MONTH==10,4:58],sum);d44month[(y-1966)*12+10,1:3]<-c(y,10,NA)
d44month[(y-1966)*12+11,4:58]<-sapply(d4465day[d4465day$YEAR==y&d4465day$MONTH==11,4:58],sum);d44month[(y-1966)*12+11,1:3]<-c(y,11,NA)
d44month[(y-1966)*12+12,4:58]<-sapply(d4465day[d4465day$YEAR==y&d4465day$MONTH==12,4:58],sum);d44month[(y-1966)*12+11,1:3]<-c(y,12,NA)
}