R help - Nov 2007 - Getting mean in a dataframe

Sorry to hijack this thread. I have a similar but slightly different  
situation. Using the original poster's example, how to elegantly get  
the mean of column V2 when column V1 is either A or C and F1 is 0?

Thanks,
Gang


On Nov 13, 2007, at 5:30 AM, Petr PIKAL wrote:
> Hi
>
> r-help-bounces@r-project.org napsal dne 13.11.2007 10:59:09:
>
>> Dear list,
>>
>> I have this dataframe
>>
>>    V1 V2 F1
>> 1  A  2  0
>> 2  A  3  0
>> 3  A  4  1
>> 4  B  3  0
>> 5  B  2  1
>> 6  C  6  0
>> 7  C  2  0
>> 8  C  6  0
>>
>> and would like to calculate a new column
>> with mean-values, following this rule
>>
>> 1. If F1 = 0 calculate the mean from V2
>> for each factor in V1.
>>
>> 2. If F1 = 1, then F1_mean = 0
>>
>> So, the new DF should look like this
>>
>>    V1 V2 F1 F1_mean
>> 1  A  2  0     2.5
>> 2  A  3  0     2.5
>> 3  A  4  1     0.0
>> 4  B  3  0     3.0
>> 5  B  2  1     0.0
>> 6  C  6  0     7.0
>> 7  C  2  0     7.0
>> 8  C  6  0     7.0
>
> I would use ave for computing mean for combination of V1 and F1 and  
> then I
> put all values of F1_mean for which F1 is 1 to 0
>
> test$F1_mean <- ave(test$V2, test$V1, factor(test$F1), FUN = mean)
> test$F1_mean[test$F1==1] <- 0
>
> Regards
> Petr
>
>>
>> Thank you for any help!
>>
>> Patrick Hausmann


	[[alternative HTML version deleted]]

Gang Chen-3 wrote:
> 
> Sorry to hijack this thread. I have a similar but slightly different  
> situation. Using the original poster's example, how to elegantly get  
> the mean of column V2 when column V1 is either A or C and F1 is 0?
> 
> 
I am not sure if this is elegant, but it works:

a=mean(mydat$V2[mydat$F1==0 & mydat$V1 %in% ("A","C")])
-- 
View this message in context:
http://www.nabble.com/Getting-mean-in-a-dataframe-tf4801030.html#a13736727
Sent from the R help mailing list archive at Nabble.com.

Hi

r-help-bounces at r-project.org napsal dne 13.11.2007 23:29:25:
> Sorry to hijack this thread. I have a similar but slightly different 
> situation. Using the original poster's example, how to elegantly get 
> the mean of column V2 when column V1 is either A or C and F1 is 0?
I do not fully understand. You want to select subset of a data frame and 
then to compute column mean?

If yes just use ?subset or construct a logical vector according to your 
condition

lll <- (V1 == "A" | V1 == "B") & F1 == 0
mean(data[lll,"V2"])

Regards
Petr

> 
> Thanks,
> Gang
> 
> 
> On Nov 13, 2007, at 5:30 AM, Petr PIKAL wrote:
> > Hi
> >
> > r-help-bounces at r-project.org napsal dne 13.11.2007 10:59:09:
> >
> >> Dear list,
> >>
> >> I have this dataframe
> >>
> >>    V1 V2 F1
> >> 1  A  2  0
> >> 2  A  3  0
> >> 3  A  4  1
> >> 4  B  3  0
> >> 5  B  2  1
> >> 6  C  6  0
> >> 7  C  2  0
> >> 8  C  6  0
> >>
> >> and would like to calculate a new column
> >> with mean-values, following this rule
> >>
> >> 1. If F1 = 0 calculate the mean from V2
> >> for each factor in V1.
> >>
> >> 2. If F1 = 1, then F1_mean = 0
> >>
> >> So, the new DF should look like this
> >>
> >>    V1 V2 F1 F1_mean
> >> 1  A  2  0     2.5
> >> 2  A  3  0     2.5
> >> 3  A  4  1     0.0
> >> 4  B  3  0     3.0
> >> 5  B  2  1     0.0
> >> 6  C  6  0     7.0
> >> 7  C  2  0     7.0
> >> 8  C  6  0     7.0
> >
> > I would use ave for computing mean for combination of V1 and F1 and 
> > then I
> > put all values of F1_mean for which F1 is 1 to 0
> >
> > test$F1_mean <- ave(test$V2, test$V1, factor(test$F1), FUN = mean)
> > test$F1_mean[test$F1==1] <- 0
> >
> > Regards
> > Petr
> >
> >>
> >> Thank you for any help!
> >>
> >> Patrick Hausmann
> 
> 
> 
>    [[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide 
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.