[R] stdev error

[Chris Evans]

Can't see your data but perhaps:

my_tbl %>%
  mutate(Bse_bwt = round(Bse_bwt * 2) / 2) %>%
  group_by(Cat, Bse_bwt) %>%
  summarize(count = n(), 
     Bse_ftv = mean(Bse_ftv), 
     stdev = if_else(count > 1,
                     sd(Bse_ftv),
                     NA_real_))
 

----- Original Message -----
> From: "Jeff Reichman" <reichmanj using sbcglobal.net>
> To: r-help using r-project.org
> Sent: Friday, 11 March, 2022 15:14:52
> Subject: [R] stdev error

> 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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-- 
Chris Evans (he/him) <chris using psyctc.org> 
Visiting Professor, UDLA, Quito, Ecuador & Honorary Professor, University of Roehampton, London, UK.
Work web site: https://www.psyctc.org/psyctc/ 
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