[R] problem with table()

[Dominik Hattrup]

Marc Schwartz schrieb:
> on 01/26/2009 12:23 PM Dominik Hattrup wrote:
>   
>> Hey everyone,
>>
>> I am looking for the easiest way to get this table
>>
>> # Table2
>> Year / 2000 / 2002 / 2004
>> Julia / 3 / 4 / 1
>> Peter / 1 / 2 / 4
>> ...   /   ...   /   ...   /   ...
>>
>> out of this one? 
>>
>> # Table1
>> name   /   year   /   cases
>> Julia   /   2000   /   1
>> Julia   /   2000   /   2  
>> Julia   /   2002   /   4
>> Peter   /   2000   /   1
>> Julia   /   2004   /   1
>> Peter   /   2004   /   2
>> Peter   /   2002   /   2
>> Peter   /   2004   /   2
>> ...   /   ...   /   ...
>>
>> Code for table1:
>> name <- c('Julia','Julia','Julia','Peter','Julia','Peter','Peter','Peter')
>> year <- c(2000,2000,2002,2000,2004,2004,2002,2004)
>> cases <- c(1,2,4,1,1,2,2,2)
>> table1 <- data.frame(name,year,cases)
>>
>> Thanks! Dominik
>>     
>
> table() generates frequencies from individual values, not from already
> tabulated data.
>
> In this case, you can use xtabs():
>
>   
>> xtabs(cases ~ name + year, data = table1)
>>     
>        year
> name    2000 2002 2004
>   Julia    3    4    1
>   Peter    1    2    4
>
>
> See ?xtabs
>
> An alternative would be to use tapply():
>
>   
>> with(table1, tapply(cases, list(name = name, year = year), sum))
>>     
>        year
> name    2000 2002 2004
>   Julia    3    4    1
>   Peter    1    2    4
>
>
> See ?tapply
>
> HTH,
>
> Marc Schwartz
>
>   
Thank You for the quick answer. Works perfect! Dominik