[R] Data-frame selection

[Jeff Newmiller]

?aggregate

in base R. Make a short function that returns the first element of a vector and give that to aggregate.

Or...

library(dplyr)
( test %>% group_by( ID, Group ) %>% summarise( Var=first( Var ) ) %>% as.data.frame )
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Sent from my phone. Please excuse my brevity.

On October 10, 2015 8:38:00 AM PDT, Cacique Samurai <caciquesamurai at gmail.com> wrote:
>Hello R-Helpers!
>
>I have a data-frame as below (dput in the end of mail) and need to
>select just the first sequence of occurrence of each "Group" in each
>"ID".
>
>For example, for ID "1" I have two sequential occurrences of T2 and
>two sequential occurrences of T3:
>
>> test [test$ID == 1, ]
>   ID Group  Var
>3   1    T2 2.94
>4   1    T2 3.23
>5   1    T2 1.40
>6   1    T2 1.62
>7   1    T2 2.43
>8   1    T2 2.53
>9   1    T2 2.25
>10  1    T3 1.66
>11  1    T3 2.86
>12  1    T3 0.53
>13  1    T3 1.66
>14  1    T3 3.24
>15  1    T3 1.34
>16  1    T2 1.86
>17  1    T2 3.03
>18  1    T3 3.63
>19  1    T3 2.78
>20  1    T3 1.49
>
>As output, I need just the first group of T2 and T3 for this ID, like:
>
> ID Group  Var
>3   1    T2 2.94
>4   1    T2 3.23
>5   1    T2 1.40
>6   1    T2 1.62
>7   1    T2 2.43
>8   1    T2 2.53
>9   1    T2 2.25
>10  1    T3 1.66
>11  1    T3 2.86
>12  1    T3 0.53
>13  1    T3 1.66
>14  1    T3 3.24
>15  1    T3 1.34
>
>For others ID I have just one occurrence or sequence of occurrence of
>each Group.
>
>I tried to use a labeling variable, but cannot figure out do this
>without many many loops..
>
>Thanks in advanced,
>
>Raoni
>
> dput (teste)
>structure(list(ID = structure(c(3L, 4L, 1L, 1L, 1L, 1L, 1L, 1L,
>1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L,
>2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L,
>2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L), .Label = c("1", "2",
>"3", "4"), class = "factor"), Group = structure(c(1L, 2L, 1L,
>1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 1L, 1L, 2L, 2L,
>2L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 1L, 1L, 1L, 1L, 2L,
>2L, 2L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 1L, 2L, 2L, 2L), .Label =
>c("T2",
>"T3"), class = "factor"), Var = c(0.32, 1.59, 2.94, 3.23, 1.4,
>1.62, 2.43, 2.53, 2.25, 1.66, 2.86, 0.53, 1.66, 3.24, 1.34, 1.86,
>3.03, 3.63, 2.78, 1.49, 2, 2.39, 1.65, 2.05, 2.75, 2.23, 1.39,
>2.66, 1.05, 2.52, 2.49, 2.97, 0.43, 1.36, 0.79, 1.71, 1.95, 2.73,
>2.73, 2.39, 2.17, 2.34, 2.42, 1.75, 0.66, 1.64, 0.24, 2.11, 2.11,
>1.18)), .Names = c("ID", "Group", "Var"), row.names = c(NA, 50L
>), class = "data.frame")
>
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