[R] [External Email] Group by and add a constant value based on a condition dply

[Christopher W Ryan]

Is the grouping beforehand necessary? Could you simply, "for all the dates
that are "4.01.2020"  and have the "Value" greater than zero  add 5 to the
"Value" "?  I may be missing something.

--Chris Ryan

On Wed, May 26, 2021 at 11:53 AM Elahe chalabi via R-help <
r-help using r-project.org> wrote:

> Hi everyone,
>
> I have the following dataframe:
>
>
>
>       structure(list(Department = c("A", "A", "A", "A", "A", "A", "A",
>      "A", "B", "B", "B", "B", "B", "B", "B", "B"), Class = c(1L, 1L,
>     1L, 1L, 2L, 2L, 2L, 2L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L), Value = c(0L,
>     100L, 800L, 800L, 0L, 300L, 1200L, 0L, 0L, 0L, 400L, 400L, 200L,
>     800L, 1200L, 0L), Date = c("1.01.2020", "2.01.2020", "3.01.2020",
>     "4.01.2020", "1.01.2020", "2.01.2020", "3.01.2020", "4.01.2020",
>     "1.01.2020", "2.01.2020", "3.01.2020", "4.01.2020", "1.01.2020",
>     "2.01.2020", "3.01.2020", "4.01.2020")), class = "data.frame",
> row.names = c(NA,
>      -16L))
>
>  using dplyr I need to group by "Depatment" and "Class" and then for all
> the dates that are "4.01.2020"  and have the "Value" greater than zero  add
> 5 to the "Value", meaning the desired dataframe will be (NewValue column) :
>
>
>
>    structure(list(Department = c("A", "A", "A", "A", "A", "A", "A",
>  "A", "B", "B", "B", "B", "B", "B", "B", "B"), Class = c(1L, 1L,
>  1L, 1L, 2L, 2L, 2L, 2L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L), Value = c(0L,
>  100L, 800L, 800L, 0L, 300L, 1200L, 0L, 0L, 0L, 400L, 400L, 200L,
>  800L, 1200L, 0L), Date = c("1.01.2020", "2.01.2020", "3.01.2020",
>  "4.01.2020", "1.01.2020", "2.01.2020", "3.01.2020", "4.01.2020",
>  "1.01.2020", "2.01.2020", "3.01.2020", "4.01.2020", "1.01.2020",
>  "2.01.2020", "3.01.2020", "4.01.2020"), NewValue = c(0L, 100L,
>  800L, 805L, 0L, 300L, 1200L, 0L, 0L, 0L, 400L, 405L, 200L, 800L,
>  1200L, 0L)), class = "data.frame", row.names = c(NA, -16L))
>
>
> Thanks a lot for any help!
> Elahe
>
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