stdev error

From: "Jeff Reichman" <reichmanj at sbcglobal.net>
To: r-help at 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




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