[R] How to use tapply with more than one variables grouped

[David Winsemius]

On Oct 23, 2012, at 1:25 PM, noobmin wrote:

>             AL  AR  CA  NY 
> Doug    250 250 250  NA 
> Jennifer  20 340 300 100 
> Michele  250 500 250  60 
> Obama    15  45 520 600 
> 
> My English is not very good, I'll try again. I want to list ALL states in
> the country where Obama had greater contribution. The table above shows the
> total contribution received by each candidate in a given state. To AL state
> obama not received more than Doug. For the AR state he received no more than
> others candidates. For the CA state he received a total of $ 520, which is
> 520>300>250>=250 and should be selected. In NY also had the largest
> contribution, $ 600, 600>100>60 and should therefore be selected.
> 
> I want to make it to the N presidency candidates and M states of the
> country. The table above is only an example.

Perhaps:

> apply(dat, 2, function(x) x["Obama"] == max(x, na.rm=TRUE) )
   AL    AR    CA    NY 
FALSE FALSE  TRUE  TRUE 

Or perhaps:
> names(dat)[ apply(dat, 2, function(x) x["Obama"] == max(x, na.rm=TRUE) ) ]
[1] "CA" "NY"

> 

> Sorry again, for me it was clear. = ( 
> Thanks
> 
> 
> 
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David Winsemius, MD
Alameda, CA, USA