dplyr (R) 中的 stderr：我做错了什么？

Question

I'm trying to calculate year-wise standard error for the variable AcrePrice. I'm running the function stderr (also tried with sd(acrePrice)/count(n)). Both of these return an error.

Here's the relevant code:

library(alr4)
library(tidyverse)

MinnLand %>% group_by(year) %>% summarize(sd(acrePrice)/count(n))
MinnLand %>% group_by(year) %>% summarize(stderr(acrePrice))

Why is there a problem? The mean and SDs are easily calculated.

Answer 1

The issue with the first function is count , which requires a data.frame, instead it would be n()

library(dplyr)
MinnLand %>%
     group_by(year) %>%
     summarize(SE = sd(acrePrice)/n(), .groups = 'drop')

-output

# A tibble: 10 x 2
#    year    SE
#   <dbl> <dbl>
# 1  2002 2.25 
# 2  2003 0.840
# 3  2004 0.742
# 4  2005 0.862
# 5  2006 0.849
# 6  2007 0.765
# 7  2008 0.708
# 8  2009 1.23 
# 9  2010 0.986
#10  2011 1.95 

---

According to ?stderr

stdin(), stdout() and stderr() are standard connections corresponding to input, output and error on the console respectively (and not necessarily to file streams).

We can use std.error from plotrix

library(plotrix)
MinnLand %>%
       group_by(year) %>%
       summarize(SE = std.error(acrePrice))

-output

# A tibble: 10 x 2
#    year    SE
#   <dbl> <dbl>
# 1  2002  53.4
# 2  2003  38.6
# 3  2004  37.0
# 4  2005  41.5
# 5  2006  39.7
# 6  2007  36.3
# 7  2008  34.9
# 8  2009  47.1
# 9  2010  42.1
#10  2011  63.6