[R] How can I calculate conditional mean in a large dataset including date data

[Vladimir Eremeev]

>
dfr<-data.frame(day=c("1/1/1970","5/1/1970","5/12/2003","31/12/2003"),temperature=c(1,-1,2,0.5))
> dfr
        day temperature
1   1/1/1970         1.0
2   5/1/1970        -1.0
3  5/12/2003         2.0
4 31/12/2003         0.5

> aggregate(dfr["temperature"],by=list(format(as.Date(dfr$day,format="%d/%m/%Y"),"%m-%Y")),mean,na.rm=TRUE)
  Group.1 temperature
1 01-1970        0.00
2 12-2003        1.25

> aggregate(dfr["temperature"],by=list(format(as.Date(dfr$Dt,format="%d/%m/%Y"),"%m")),mean,na.rm=TRUE)
  Group.1 temperature
1      01        0.00
2      12        1.25


Majid Iravani wrote:
> 
> Dear R users,
> 
> I have a dataframe with two columns: first column is date data (e.g. 
> 1/1/2000 with character format: daily data from 1/1/1970 till 31/12/2003) 
> and second column is temperature value. Now I'd like to calculate mean for 
> each month in a year (i.e. May 2001, June 1997) and mean for each month in 
> all of years. As the number of days in some months is different from
> others 
> I could not write appreciate command for this. Therefore I would greatly 
> appreciate if somebody can help me in this case
> 
> Thank you
> Majid
> 
> 

-- 
View this message in context: http://www.nabble.com/-R--How-can-I-calculate-conditional-mean-in-a-large-dataset-including-date-data-tf3154751.html#a8748821
Sent from the R help mailing list archive at Nabble.com.