Hi -
I am trying to find and describe missing data in a time series. For instance,
in the library openair, there is a data frame called "mydata":
library(openair)
head(mydata)
date ws wd nox no2 o3 pm10 so2 co pm25
1 1998-01-01 00:00:00 0.60 280 285 39 1 29 4.7225 3.3725 NA
2 1998-01-01 01:00:00 2.16 230 NA NA NA 37 NA NA NA
3 1998-01-01 02:00:00 2.76 190 NA NA 3 34 6.8300 9.6025 NA
4 1998-01-01 03:00:00 2.16 170 493 52 3 35 7.6625 10.2175 NA
5 1998-01-01 04:00:00 2.40 180 468 78 2 34 8.0700 8.9125 NA
6 1998-01-01 05:00:00 3.00 190 264 42 0 16 5.5050 3.0525 NA
So for example, I would like to be able to detect for pm25, I would like to be
able to detect that there are NA's starting at 1998-01-01 0:00:00 and runs for
2887 hourly observations. Then I would be able to know that there is an NA at
2910 and so on. The key information I am looking for is when the NA's start and
their length. The closest thing I can use that I know about is timePlot in the
openair package with statistic="frequency" but it only gives monthly summary
data, and does not tell me if the missing data are clumped together or are
dispersed.
VR
Jim
James T. Durant, MSPH CIH
Emergency Response Coordinator
US Agency for Toxic Substances and Disease Registry
Atlanta, GA 30341
770-378-1695
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