R help - Dec 2021 - Find tibble row with maximum recorded value

Hello,

Inline.

?s 22:08 de 03/12/21, Rich Shepard escreveu:
> On Fri, 3 Dec 2021, Rich Shepard wrote:
> 
>> I find solutions when the data_frame is grouped, but none when it's
not.
> 
> Thanks, Bert. ?which.max confirmed that's all I need to find the
maximum
> value.
> 
> Now I need to read more than ?filter to learn why I'm not getting the
> relevant row with:
>> which.max(pdx_disc$cfs)
> [1] 8054
This is the *index* for which cfs is the first maximum, not the maximum 
value itself.
> 
>> filter(pdx_disc, cfs == 8054)
Therefore, you probably want any of


filter(pdx_disc, cfs == cfs[8054])

filter(pdx_disc, cfs == cfs[which.max(cfs)])

filter(pdx_disc, cfs == max(cfs))    # I find this one better, simpler


Hope this helps,

Rui Barradas

> # A tibble: 0 ? 9
> # ? with 9 variables: site_nbr <chr>, year <int>, mon
<int>, day <int>,
> #?? hr <dbl>, min <dbl>, tz <chr>, cfs <dbl>,
sampdt <dttm>
> 
> Regards,
> 
> Rich
> 
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide 
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

On Fri, 3 Dec 2021, Rui Barradas wrote:
>> which.max(pdx_disc$cfs)
>> [1] 8054
> This is the *index* for which cfs is the first maximum, not the maximum
> value itself.
Rui,

Mea culpa! I completely forgot this.
> Therefore, you probably want any of
> filter(pdx_disc, cfs == cfs[8054])
> filter(pdx_disc, cfs == cfs[which.max(cfs)])
> filter(pdx_disc, cfs == max(cfs))    # I find this one better, simpler
> Hope this helps,
Yes, it does.

Thank you very much,

Rich

Perhaps you meant to point this out, but the cfs[which.max(cfs)] and
cfs == ... are not the same:
> x <- rep(1:2,3)
> x
[1] 1 2 1 2 1 2
> x[which.max(x)]
[1] 2
> x[x==max(x)]
[1] 2 2 2

So maybe your point is: which does the OP want (in case there are
repeated maxes)? I suspect the == forms, but ...?

Bert Gunter

On Fri, Dec 3, 2021 at 2:56 PM Rui Barradas <ruipbarradas at sapo.pt>
wrote:
>
> Hello,
>
> Inline.
>
> ?s 22:08 de 03/12/21, Rich Shepard escreveu:
> > On Fri, 3 Dec 2021, Rich Shepard wrote:
> >
> >> I find solutions when the data_frame is grouped, but none when
it's not.
> >
> > Thanks, Bert. ?which.max confirmed that's all I need to find the
maximum
> > value.
> >
> > Now I need to read more than ?filter to learn why I'm not getting
the
> > relevant row with:
> >> which.max(pdx_disc$cfs)
> > [1] 8054
>
> This is the *index* for which cfs is the first maximum, not the maximum
> value itself.
>
> >
> >> filter(pdx_disc, cfs == 8054)
>
> Therefore, you probably want any of
>
>
> filter(pdx_disc, cfs == cfs[8054])
>
> filter(pdx_disc, cfs == cfs[which.max(cfs)])
>
> filter(pdx_disc, cfs == max(cfs))    # I find this one better, simpler
>
>
> Hope this helps,
>
> Rui Barradas
>
>
> > # A tibble: 0 ? 9
> > # ? with 9 variables: site_nbr <chr>, year <int>, mon
<int>, day <int>,
> > #   hr <dbl>, min <dbl>, tz <chr>, cfs <dbl>,
sampdt <dttm>
> >
> > Regards,
> >
> > Rich
> >
> > ______________________________________________
> > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide
> > http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.