Вот один подход:
dat <- read.table(text="Jan 4 2004, 0.99
Jan 11 2004, 1.11
Jan 18 2004, 1.06", header=F)
dat
dat2 <- dat[rep(seq_len(nrow(dat)), 7), ]
dat2 <- with(dat2, dat2[order(V1, V2, V3), ])
dat2$V2 <- rep(dat$V2, each=7) + 0:6
rownames(dat2) <- 1:nrow(dat2)
dat2
Что дает:
V1 V2 V3 V4
1 Jan 4 2004, 0.99
2 Jan 5 2004, 0.99
3 Jan 6 2004, 0.99
4 Jan 7 2004, 0.99
5 Jan 8 2004, 0.99
6 Jan 9 2004, 0.99
7 Jan 10 2004, 0.99
8 Jan 11 2004, 1.11
9 Jan 12 2004, 1.11
10 Jan 13 2004, 1.11
11 Jan 14 2004, 1.11
12 Jan 15 2004, 1.11
13 Jan 16 2004, 1.11
14 Jan 17 2004, 1.11
15 Jan 18 2004, 1.06
16 Jan 19 2004, 1.06
17 Jan 20 2004, 1.06
18 Jan 21 2004, 1.06
19 Jan 22 2004, 1.06
20 Jan 23 2004, 1.06
21 Jan 24 2004, 1.06