5th of month working day

Hello,

I have a daily data zoo object with ?prices such as:

05/04/2006 ? ? ?1311.56
06/04/2006 ? ? ?1309.04
07/04/2006 ? ? ?1295.5
10/04/2006 ? ? ?1296.6
11/04/2006 ? ? ?1286.57
12/04/2006 ? ? ?1288.12
13/04/2006 ? ? ?1289.12
14/04/2006 ? ? ?1289.12
17/04/2006 ? ? ?1285.33
18/04/2006 ? ? ?1307.65
19/04/2006 ? ? ?1309.93
20/04/2006 ? ? ?1311.46
21/04/2006 ? ? ?1311.28
24/04/2006 ? ? ?1308.11
25/04/2006 ? ? ?1301.74
26/04/2006 ? ? ?1305.41
27/04/2006 ? ? ?1309.72
28/04/2006 ? ? ?1310.61
01/05/2006 ? ? ?1305.19
02/05/2006 ? ? ?1313.21
03/05/2006 ? ? ?1307.85
04/05/2006 ? ? ?1312.25
05/05/2006 ? ? ?1325.76



How can I isolate the 5th day of each month (if this was a
working/trading day) otherwise the most recent (before the 5th) working
day for each month?

Your sample data always has the 5th of the month filled in but
assuming that that is not the case for the real data, merge your
series with a zero width series having every date and use na.locf to
move values up into subsequent NAs.  Then just pick off the 5th of
each month.

Lines <- "05/04/2006      1311.56
06/04/2006      1309.04
07/04/2006      1295.5
10/04/2006      1296.6
11/04/2006      1286.57
12/04/2006      1288.12
13/04/2006      1289.12
14/04/2006      1289.12
17/04/2006      1285.33
18/04/2006      1307.65
19/04/2006      1309.93
20/04/2006      1311.46
21/04/2006      1311.28
24/04/2006      1308.11
25/04/2006      1301.74
26/04/2006      1305.41
27/04/2006      1309.72
28/04/2006      1310.61
01/05/2006      1305.19
02/05/2006      1313.21
03/05/2006      1307.85
04/05/2006      1312.25
05/05/2006      1325.76"
library(zoo)
z <- read.zoo(textConnection(Lines), format = "%d/%m/%Y")
rng <- range(time(z))
zz <- na.locf(merge(z, zoo(, seq(rng[1], rng[2], by = "day"))))
zz[format(time(zz), "%d") == "05"]