[R] stdev error
Rui Barradas
ru|pb@rr@d@@ @end|ng |rom @@po@pt
Fri Mar 11 16:24:03 CET 2022
Hello,
I cannot reproduce this error with a built-in data set.
Can you post str(my_tbl)?
suppressPackageStartupMessages(library(dplyr))
mtcars %>%
mutate(hp = round(hp * 2) / 2) %>%
group_by(cyl, hp) %>%
summarise(
count = n(),
hp = mean(hp),
stdev = sd(hp)
)
#> `summarise()` has grouped output by 'cyl'. You can override using the
`.groups`
#> argument.
#> # A tibble: 23 x 4
#> # Groups: cyl [3]
#> cyl hp count stdev
#> <dbl> <dbl> <int> <dbl>
#> 1 4 52 1 NA
#> 2 4 62 1 NA
#> 3 4 65 1 NA
#> 4 4 66 2 NA
#> 5 4 91 1 NA
#> 6 4 93 1 NA
#> 7 4 95 1 NA
#> 8 4 97 1 NA
#> 9 4 109 1 NA
#> 10 4 113 1 NA
#> # ... with 13 more rows
Hope this helps,
Rui Barradas
Às 14:14 de 11/03/2022, Jeff Reichman escreveu:
> r-help forum
>
>
>
> When I run the following code
>
>
>
> my_tbl %>%
>
> mutate(Bse_bwt = round(Bse_bwt * 2) / 2) %>%
>
> group_by(Cat, Bse_bwt) %>%
>
> summarize(count = n(), Bse_ftv = mean(Bse_ftv), stdev = sd(Bse_ftv))
>
>
>
> I get the following error:
>
>
>
> Error: `stdev` refers to a variable created earlier in this summarise().
>
> Do you need an extra mutate() step?
>
>
>
> I suspect it is because the standard deviation of a length-one vector is NA
> and R is errorerrors out on the standard deviation of 1. So then I tried
>
>
>
> summarize(count = n(), Bse_ftv = mean(Bse_ftv), stdev = if(n()>1)
> sd(Bse_ftv) else 0) and this didn't seem to work either. So there has to be
> a way to add some sort of error checker to my standard deviation function to
> check if n > 1 and then take the standard deviation in dplyr.
>
>
>
> Jeff
>
>
>
>
> [[alternative HTML version deleted]]
>
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