r - Mean/sd: Figure out the mean and standard deviation for each group. And then the one closer to one of the groups is assigned that

Question

This is my data.

I'm trying to figure out the mean/sd of groups A and groups B, but I'm at a loss:

library(ggplot2)
n <- 10000
df <- data.frame(
  cats=rep(c("A","B"), each=n), 
  vals=c(rnorm(n, mean=10, sd=2), rnorm(n, mean=20, sd=2))
)
ggplot(df, aes(vals, color=cats)) +
  geom_density()

标签： rstatisticsprobability

Answer 1

您可以使用 dplyr::summarize

library(dplyr)
df %>% group_by(cats) %>% summarize(sd = sd(vals), mean = mean(vals))

cats     sd  mean
<fct> <dbl> <dbl>
1 A      1.99  10.0
2 B      1.98  20.0