Try this:

with(data1, table(ID, Year))

On Tue, Oct 14, 2008 at 10:58 AM, Tom La Bone <booboo@gforcecable.com>wrote:

>
> Assume that I have the dataframe "data1", which is listed at the end of
> this
> message. I want count the number of lines that each person has for each
> year. For example, the person with ID=213 has 15 entries (NinYear) for
> 1953.
> The following bit of code calculates NinYear:
>
> for (i in 1:length(data1$ID)) {
>  data1$NinYear[i] <- length(data1[data1$Year==data1$Year[i] &
>    data1$ID==data1$ID[i],1]) }
>
> This seems to work but is horribly slow (some files I am working with have
> over 500,000 lines). Can anyone suggest a faster way of doing this, perhaps
> a way that does not use a for loop? Thanks.
>
> Tom
>
> ID      Year    NinYear
> 209     1971    0
> 209     1971    0
> 213     1951    0
> 213     1951    0
> 213     1953    0
> 213     1953    0
> 213     1953    0
> 213     1953    0
> 213     1953    0
> 213     1953    0
> 213     1953    0
> 213     1953    0
> 213     1953    0
> 213     1953    0
> 213     1953    0
> 213     1953    0
> 213     1953    0
> 213     1953    0
> 213     1953    0
> 213     1954    0
> 213     1954    0
> 213     1954    0
> 213     1954    0
> 213     1954    0
> 213     1954    0
> 213     1954    0
> 213     1954    0
> 213     1954    0
> 213     1954    0
> 213     1954    0
> 213     1955    0
> 213     1955    0
> 234     1953    0
> 234     1953    0
> 234     1953    0
> 234     1953    0
> 234     1953    0
> 234     1958    0
> 234     1958    0
> 234     1965    0
> 234     1965    0
> 234     1965    0
> 249     1952    0
> 249     1952    0
>
>
>
> --
> View this message in context:
> http://www.nabble.com/Doing-a-Task-Without-Using-a-For-Loop-tp19974078p19974078.html
> Sent from the R help mailing list archive at Nabble.com.
>
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> and provide commented, minimal, self-contained, reproducible code.
>



-- 
Henrique Dallazuanna
Curitiba-Paraná-Brasil
25° 25' 40" S 49° 16' 22" O

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