[R] Getting minimum value of a column according a factor column of a dataframe
Bill Dunlap
w||||@mwdun|@p @end|ng |rom gm@||@com
Thu Aug 25 18:05:26 CEST 2022
The order of the rows returned by summarize is controlled by the levels of
the factors given to group_by. If group_by is given character columns
instead of factors, it converts them to factors with the levels being the
sorted unique values of the character columns. Convert you character
columns to factors with the desired levels to get the order you want.
E.g.,
> d <- data.frame(charGroup=rep(c("Small","Medium","Large"),3:1), x=101:106)
> d$factorGroup <- factor(d$charGroup, levels=c("Small","Medium","Large","X
Large"))
> d
charGroup x factorGroup
1 Small 101 Small
2 Small 102 Small
3 Small 103 Small
4 Medium 104 Medium
5 Medium 105 Medium
6 Large 106 Large
> d |> group_by(charGroup) |> summarize(minX=min(x))
# A tibble: 3 × 2
charGroup minX
<chr> <int>
1 Large 106
2 Medium 104
3 Small 101
> d |> group_by(factorGroup) |> summarize(minX=min(x))
# A tibble: 3 × 2
factorGroup minX
<fct> <int>
1 Small 101
2 Medium 104
3 Large 106
> # .drop=FALSE outputs a row for each unused level as well
> d |> group_by(factorGroup, .drop=FALSE) |> summarize(minX=min(x))
# A tibble: 4 × 2
factorGroup minX
<fct> <dbl>
1 Small 101
2 Medium 104
3 Large 106
4 X Large Inf
Warning message:
In min(x) : no non-missing arguments to min; returning Inf
-Bill
On Thu, Aug 25, 2022 at 4:05 AM javad bayat <j.bayat194 using gmail.com> wrote:
> Dear Rui;
> Thank you very much. Both of your codes worked correctly. Now I can see the
> whole row's value.
> But I found a problem in the results. When I run your codes, the results
> are shown in a sorted table. I do not know why the results have been sorted
> according to the "Code" column, smallest to largest. Is there any way to
> get the results like their order in the first data frame (bilan2)? I used
> your codes as follow:
>
> > bilan3 <- lapply(split(bilan2, bilan2$Code), \(x) x[which.min(x$Q),])
> > bilan3 = data.frame(do.call(rbind, bilan3))
> Sincerely
>
>
>
> On Thu, Aug 25, 2022 at 11:52 AM Rui Barradas <ruipbarradas using sapo.pt>
> wrote:
>
> > Hello,
> >
> > OK, what about
> >
> >
> > res <- lapply(split(df1, df1$Code), \(x) x[which.min(x$Q),])
> > do.call(rbind, res)
> > # Code Y M D Q N O
> > # 41003 41003 81 1 19 0.160 7.17 2.50
> > # 41005 41005 79 8 17 0.210 5.50 7.20
> > # 41009 41009 79 2 21 0.218 5.56 4.04
> > # 41017 41017 79 10 20 0.240 5.30 7.10
> >
> >
> > A dplyr solution.
> >
> >
> >
> > suppressPackageStartupMessages(library(dplyr))
> >
> > df1 %>%
> > group_by(Code) %>%
> > slice_min(Q) %>%
> > slice_head(n = 1)
> > # # A tibble: 4 × 7
> > # # Groups: Code [4]
> > # Code Y M D Q N O
> > # <fct> <int> <int> <int> <dbl> <dbl> <dbl>
> > # 1 41003 81 1 19 0.16 7.17 2.5
> > # 2 41005 79 8 17 0.21 5.5 7.2
> > # 3 41009 79 2 21 0.218 5.56 4.04
> > # 4 41017 79 10 20 0.24 5.3 7.1
> >
> >
> >
> > Hope this helps,
> >
> > Rui Barradas
> >
> >
> > Às 05:56 de 25/08/2022, javad bayat escreveu:
> > > Dear all,
> > > Many thanks for your suggested methods and codes, but unfortunately
> they
> > > did not give the desired results.
> > > All the codes you have provided are correct but they did not represent
> > the
> > > whole row which is related to the minimum of "Q".
> > > The code must result in 4 rows, with the minimum value of "Q" and other
> > > column values, as below:
> > >
> > > Code
> > >
> > > Y
> > >
> > > M
> > >
> > > D
> > >
> > > Q
> > >
> > > N
> > >
> > > O
> > >
> > > 41003
> > >
> > > 81
> > >
> > > 1
> > >
> > > 19
> > >
> > > 0.16
> > >
> > > 7.17
> > >
> > > 2.5
> > >
> > > 41005
> > >
> > > 79
> > >
> > > 8
> > >
> > > 17
> > >
> > > 0.21
> > >
> > > 5.5
> > >
> > > 7.2
> > >
> > > 41009
> > >
> > > 79
> > >
> > > 2
> > >
> > > 21
> > >
> > > 0.218
> > >
> > > 5.56
> > >
> > > 4.04
> > > 41017 79 10 20 0.24 5.3 7.1
> > >
> > >
> > >
> > >
> > >
> > >
> > > Sincerely
> > >
> > >
> > >
> > >
> > >
> > >
> > >
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> > > 41017 79 10 20 0.24 5.3 7.1
> > >
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> > >
> > > On Wed, Aug 24, 2022 at 9:24 PM Rui Barradas <ruipbarradas using sapo.pt>
> > wrote:
> > >
> > >> Hello,
> > >>
> > >> Here are two options, the 1st outputs a vector, the 2nd a data.frame.
> > >>
> > >>
> > >> x<-'41003 81 1 19 0.16 7.17 2.5
> > >> 41003 77 9 22 0.197 6.8 2.2
> > >> 41003 79 7 28 0.21 4.7 6.2
> > >> 41005 79 8 17 0.21 5.5 7.2
> > >> 41005 80 10 30 0.21 6.84 2.6
> > >> 41005 80 12 20 0.21 6.84 2.4
> > >> 41005 79 6 14 0.217 5.61 3.55
> > >> 41009 79 2 21 0.218 5.56 4.04
> > >> 41009 79 5 27 0.218 6.4 3.12
> > >> 41009 80 11 29 0.22 6.84 2.8
> > >> 41009 78 5 28 0.232 6 3.2
> > >> 41009 81 8 20 0.233 6.39 1.6
> > >> 41009 79 9 30 0.24 5.6 7.5
> > >> 41017 79 10 20 0.24 5.3 7.1
> > >> 41017 80 7 30 0.24 6.73 2.6'
> > >> df1 <- read.table(textConnection(x))
> > >> names(df1) <- scan(what = character(),
> > >> text = 'Code Y M D Q N O')
> > >> df1$Code <- factor(df1$Code)
> > >>
> > >> # 1st option
> > >> with(df1, tapply(Q, Code, min))
> > >> # 41003 41005 41009 41017
> > >> # 0.160 0.210 0.218 0.240
> > >>
> > >> # 2nd option
> > >> aggregate(Q ~ Code, df1, min)
> > >> # Code Q
> > >> # 1 41003 0.160
> > >> # 2 41005 0.210
> > >> # 3 41009 0.218
> > >> # 4 41017 0.240
> > >>
> > >>
> > >> Hope this helps,
> > >>
> > >> Rui Barradas
> > >>
> > >> Às 08:44 de 24/08/2022, javad bayat escreveu:
> > >>> Dear all;
> > >>> I am trying to get the minimum value of a column based on a factor
> > column
> > >>> of the same data frame. My data frame is like the below:
> > >>> Code Y M D
> > >>> Q
> > >>> N O
> > >>> 41003 81 1 19 0.16 7.17 2.5
> > >>> 41003 77 9 22 0.197 6.8 2.2
> > >>> 41003 79 7 28 0.21 4.7 6.2
> > >>> 41005 79 8 17 0.21 5.5 7.2
> > >>> 41005 80 10 30 0.21 6.84 2.6
> > >>> 41005 80 12 20 0.21 6.84 2.4
> > >>> 41005 79 6 14 0.217 5.61 3.55
> > >>> 41009 79 2 21 0.218 5.56 4.04
> > >>> 41009 79 5 27 0.218 6.4 3.12
> > >>> 41009 80 11 29 0.22 6.84 2.8
> > >>> 41009 78 5 28 0.232 6 3.2
> > >>> 41009 81 8 20 0.233 6.39 1.6
> > >>> 41009 79 9 30 0.24 5.6 7.5
> > >>> 41017 79 10 20 0.24 5.3 7.1
> > >>> 41017 80 7 30 0.24 6.73 2.6
> > >>>
> > >>> I want to get the minimum value of the "Q" column with the whole row
> > >>> values, according to the "Code" column which is a factor. Overall
> it
> > >> will
> > >>> give me 4 rows, with the value of "Q". Below is a code that I used
> but
> > it
> > >>> did not give me what I wanted.
> > >>>
> > >>>> x[which(x$Q == min(x$Q)),]
> > >>>
> > >>> Sincerely
> > >>>
> > >>>
> > >>>
> > >>
> > >
> > >
> >
>
>
> --
> Best Regards
> Javad Bayat
> M.Sc. Environment Engineering
> Alternative Mail: bayat194 using yahoo.com
>
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>
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