R 3.3.1
OS X
Colleagues,
I have two large data frames that I am trying to link efficiently. A small
example is as follows:
structure(list(Day = c(1L, 2L, 3L, 5L, 6L, 7L, 8L, 9L, 10L, 11L,
13L, 14L, 16L, 17L, 18L, 19L, 20L, 21L, 22L, 23L, 24L, 25L, 26L,
27L, 28L, 29L, 30L), Value = c(76, 116, 111, 103, 114, 99, 128,
96, 81, 84, 81, 108, 109, 106, 125, 128, 92, 90, 83, 89, 76,
89, 101, 93, 98, 77, 92)), .Names = c("Day", "Value"), row.names = c(NA,
-27L), class = "data.frame")
which becomes:
Day Value
1 1 76
2 2 116
3 3 111
4 5 103
5 6 114
6 7 99
7 8 128
8 9 96
9 10 81
10 11 84
11 13 81
12 14 108
13 16 109
14 17 106
15 18 125
16 19 128
17 20 92
18 21 90
19 22 83
20 23 89
21 24 76
22 25 89
23 26 101
24 27 93
25 28 98
26 29 77
27 30 92
The second dataframe is merely:
TESTDAYS <- data.frame(TestDay = c(4, 11, 15))
For each row in the second dataframe, I would like to identify the first row in
the first dataframe in which Day is >= TestDay.
For example, for TestDay == 4, Day would equal 5. I would then append the
corresponding “Value” in the TestValue column
The result would be:
TestDay TestValue
1 4 103
2 11 84
3 15 109
I can accomplish this with brute force but I suspect that there is some clever
day to vectorize this. Any help would be appreciated.
Dennis
Dennis Fisher MD
P < (The "P Less Than" Company)
Phone / Fax: 1-866-PLessThan (1-866-753-7784)
www.PLessThan.com <http://www.plessthan.com/>
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