[R] Find tibble row with maximum recorded value

Bert Gunter
Fri, 03 Dec 2021 21:21:34 -0000

which.max(dat$cfs), I presume.
see ?which.max

(as usual, true tidyverse questions belong on RStudio's help site, not
here).

Bert Gunter

"The trouble with having an open mind is that people keep coming along
and sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )

On Fri, Dec 3, 2021 at 12:56 PM Rich Shepard <rshepard at appl-ecosys.com>
wrote:
>
> I find solutions when the data_frame is grouped, but none when it's
not.
>
> The data:
> # A tibble: 813,693 ? 9
>     site_nbr  year   mon   day    hr   min tz      cfs sampdt
>     <chr>    <int> <int> <int> <dbl>
<dbl> <chr> <dbl> <dttm>
>   1 14211720  1988    10     1     0    10 PDT   16800 1988-10-01 00:10:00
>   2 14211720  1988    10     1     0    20 PDT   16800 1988-10-01 00:20:00
>   3 14211720  1988    10     1     0    30 PDT   17300 1988-10-01 00:30:00
>   4 14211720  1988    10     1     0    40 PDT   18200 1988-10-01 00:40:00
>   5 14211720  1988    10     1     0    50 PDT   18100 1988-10-01 00:50:00
>   6 14211720  1988    10     1     1     0 PDT   18400 1988-10-01 01:00:00
>   7 14211720  1988    10     1     1    10 PDT   18700 1988-10-01 01:10:00
>   8 14211720  1988    10     1     1    20 PDT   19200 1988-10-01 01:20:00
>   9 14211720  1988    10     1     1    30 PDT   19200 1988-10-01 01:30:00
> 10 14211720  1988    10     1     1    40 PDT   18900 1988-10-01 01:40:00
> # ? with 813,683 more rows
>
> The script:
> library(tidyverse)
>
> max_pdx_disc <- pdx_disc %>%
>      summarize(max_cfs = max(cfs), max_cfs_sampdt = cfs(which.max(cfs)))
>
> The error:
> > source('../scripts/filter_by_column_max.r')
> Error: Problem with `summarise()` column `max_cfs_sampdt`.
>   `max_cfs_sampdt = sampt(which.max(cfs))`.
>   could not find function "sampt"
> > Run `rlang::last_error()` to see where the error occurred.
>
> I looked at the the last_error and the traceback without understanding how
> to filter the row with the maximum cfs value.
>
> What do I read to learn how to return this row?
>
> TIA,
>
> Rich
>
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