[R] dplyr - counting a number of specific values in each column - for all columns at once

Dimitri Liakhovitski dimitri.liakhovitski at gmail.com
Tue Jun 16 19:56:11 CEST 2015


Thank you, Bert.
I'll be honest - I am just learning dplyr and was wondering if one
could do it in dplyr.
But of course your solution is perfect...

On Tue, Jun 16, 2015 at 1:50 PM, Bert Gunter <bgunter.4567 at gmail.com> wrote:
> Well, dplyr seems a bit of overkill as it's so simple with plain old
> vapply() in base R :
>
>
>> dat <- data.frame (a=sample(1:5,10,rep=TRUE),
> +                    b=sample(3:7,10,rep=TRUE),
> +                    g = sample(7:9,10,rep=TRUE))
>
>> vapply(dat,function(x)sum(x==5,na.rm=TRUE),1L)
>
> a b g
> 5 4 0
>
>
>
> Cheers,
> Bert
>
> Bert Gunter
>
> "Data is not information. Information is not knowledge. And knowledge is
> certainly not wisdom."
>    -- Clifford Stoll
>
> On Tue, Jun 16, 2015 at 10:24 AM, Dimitri Liakhovitski
> <dimitri.liakhovitski at gmail.com> wrote:
>>
>> Hello!
>>
>> I have a data frame:
>>
>> md <- data.frame(a = c(3,5,4,5,3,5), b = c(5,5,5,4,4,1), c =
>> c(1,3,4,3,5,5),
>>       device = c(1,1,2,2,3,3))
>> myvars = c("a", "b", "c")
>> md[2,3] <- NA
>> md[4,1] <- NA
>> md
>>
>> I want to count number of 5s in each column - by device. I can do it like
>> this:
>>
>> library(dplyr)
>> group_by(md, device) %>%
>> summarise(counts.a = sum(a==5, na.rm = T),
>>           counts.b = sum(b==5, na.rm = T),
>>           counts.c = sum(c==5, na.rm = T))
>>
>> However, in real life I'll have tons of variables (the length of
>> 'myvars' can be very large) - so that I can't specify those counts.a,
>> counts.b, etc. manually - dozens of times.
>>
>> Does dplyr allow to run the count of 5s on all 'myvars' columns at once?
>>
>>
>> --
>> Dimitri Liakhovitski
>>
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>
>



-- 
Dimitri Liakhovitski



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