Hi:
There is a months() function associated with Date objects, so you should be
able to do something like
aggregate(value ~ months(date), data = data$flow$daily, FUN = median)
Here's a toy example because your data are not in a ready form:
df <- data.frame(date = seq(as.Date('2010-01-01'), by = 'days', length =
250),
val = rnorm(250))
> aggregate(val ~ months(date), data = df, FUN = median)
months(date) val
1 April -0.18864817
2 August -0.16203705
3 February 0.03671700
4 January 0.04500988
5 July -0.12753151
6 June 0.09864811
7 March 0.23652105
8 May 0.25879994
9 September 0.53570764
HTH,
Dennis
On Sun, Dec 19, 2010 at 2:31 PM, HUXTERE <[email protected]> wrote:
>
> Hello,
>
> I have a multi-year dataset (see below) with date, a data value and a flag
> for the data value. I want to find the monthly median for each month in
> this
> dataset and then plot it. If anyone has suggestions they would be greatly
> apperciated. It should be noted that there are some dates with no values
> and
> they should be removed.
>
> Thanks
> Emily
>
> > print ( str(data$flow$daily) )
> 'data.frame': 16071 obs. of 3 variables:
> $ date :Class 'Date' num [1:16071] -1826 -1825 -1824 -1823 -1822 ...
> $ value: num NA NA NA NA NA NA NA NA NA NA ...
> $ flag : chr "" "" "" "" ...
> NULL
>
> 520 2008-11-01 0.034
> 1041 2008-11-02 0.034
> 1562 2008-11-03 0.034
> 2083 2008-11-04 0.038
> 2604 2008-11-05 0.036
> 3125 2008-11-06 0.035
> 3646 2008-11-07 0.036
> 4167 2008-11-08 0.039
> 4688 2008-11-09 0.039
> 5209 2008-11-10 0.039
> 5730 2008-11-11 0.038
> 6251 2008-11-12 0.039
> 6772 2008-11-13 0.039
> 7293 2008-11-14 0.038
> 7814 2008-11-15 0.037
> 8335 2008-11-16 0.037
> 8855 2008-11-17 0.037
> 9375 2008-11-18 0.037
> 9895 2008-11-19 0.034 B
> 10415 2008-11-20 0.034 B
> 10935 2008-11-21 0.033 B
> 11455 2008-11-22 0.034 B
> 11975 2008-11-23 0.034 B
> 12495 2008-11-24 0.034 B
> 13016 2008-11-25 0.034 B
> 13537 2008-11-26 0.033 B
> 14058 2008-11-27 0.033 B
> 14579 2008-11-28 0.033 B
> 15068 2008-11-29 0.034 B
> 15546 2008-11-30 0.035 B
> 521 2008-12-01 0.035 B
> 1042 2008-12-02 0.034 B
> 1563 2008-12-03 0.033 B
> 2084 2008-12-04 0.031 B
> 2605 2008-12-05 0.031 B
> 3126 2008-12-06 0.031 B
> 3647 2008-12-07 0.032 B
> 4168 2008-12-08 0.032 B
> 4689 2008-12-09 0.032 B
> 5210 2008-12-10 0.033 B
> 5731 2008-12-11 0.033 B
> 6252 2008-12-12 0.032 B
> 6773 2008-12-13 0.031 B
> 7294 2008-12-14 0.030 B
> 7815 2008-12-15 0.030 B
> 8336 2008-12-16 0.029 B
> 8856 2008-12-17 0.028 B
> 9376 2008-12-18 0.028 B
> 9896 2008-12-19 0.028 B
> 10416 2008-12-20 0.027 B
> 10936 2008-12-21 0.027 B
> 11456 2008-12-22 0.028 B
> 11976 2008-12-23 0.028 B
> 12496 2008-12-24 0.029 B
> 13017 2008-12-25 0.029 B
> 13538 2008-12-26 0.029 B
> 14059 2008-12-27 0.030 B
> 14580 2008-12-28 0.030 B
> 15069 2008-12-29 0.030 B
> 15547 2008-12-30 0.031 B
> 15851 2008-12-31 0.031 B
> --
> View this message in context:
> http://r.789695.n4.nabble.com/monthly-median-in-a-daily-dataset-tp3094917p3094917.html
> Sent from the R help mailing list archive at Nabble.com.
>
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