[R] extracting monthly temperature data

Spencer Graves
Sun, 07 Sep 2003 19:01:42 -0000

What is "class(temp.dat)"?  Have you considered
"?data.frame"?  If
"temp.dat" is a data.frame, you can recombine date.time with Temp via

	  temp.dat$date.time <- date.time.

	  Then you can "rm(date.time)", because the above command makes a
copy
as a column of the data.frame temp.dat.

	  I have not been working with POSIXt, so I can't answer your question
about how to get monthly means, other than to ask if you know about
subscripting with a logical vector, "aggregate" and
"tapply"?

hope this helps.  spencer graves

Andy Bunn wrote:
> I know that R is very advanced when it comes to DateTime handling. I am
> not quite as advanced as R however.
>
> I just downloaded a stupendously ugly dataset of hourly air temperature
> from 1985 to 2003. It has a great many NAs. I want to extract mean,
> median, max, and min monthly values.
>
> So far I have read it in as object. Date and Time are factors and Temp
> is an int.
>
>
>>summary(temp.dat)
>
>          Date             Time             Temp
>  01/01/1986:    24   03:00  :  6457   Min.   :  -22.00
>  01/01/1987:    24   04:00  :  6457   1st Qu.:   23.00
>  01/01/1988:    24   05:00  :  6457   Median :   34.00
>  01/01/1989:    24   06:00  :  6457   Mean   :   34.35
>  01/01/1990:    24   10:00  :  6457   3rd Qu.:   45.00
>  01/01/1992:    24   11:00  :  6457   Max.   :   89.00
>  (Other)   :154794   (Other):116196   NA's   :52178.00
>
> I then made a POSIXt object for the dates and times.
>
>
>>date.time <- strptime(paste(temp.dat$Date, temp.dat$Time),
"%m/%d/%Y
>
> %H:")
>
>>class(date.time)
>
> [1] "POSIXt"  "POSIXlt"
>
>>date.time[1]
>
> [1] "1985-10-01 01:00:00"
>
>
> Now I'm stuck.
>
> Questions:
>
> What's the best class for reuniting the temperature data with the
dates?
> A time series? A list?
>
> Depending on the answer, what's the best way to extract, say, the mean
> temperatures for Sepetmber?
>
> Thanks in advance, Andy
>
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