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
>
> [EMAIL PROTECTED] 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
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