如何在 R 中计算特定条件下的平均值？

Question

I've been trying to calculate the average of a column with condition in a dataframe and plot it in a graph. But so far I can only get the average of the whole column with mean(df$Age) . Sample dataframe

What I'm trying to get is the average age of employees in Vancouver but I'm not sure how to do it so I can't plot it out.

Answer 1

library(tidyverse)
tribble(
  ~Age, ~City,
  61, "Vancouver",
  58, "Vancouver",
  48, "Terrace",
  48, "Terrace"
) %>%
  group_by(City) %>%
  summarise(Age = mean(Age))
#> # A tibble: 2 x 2
#>   City        Age
#>   <chr>     <dbl>
#> 1 Terrace    48  
#> 2 Vancouver  59.5

^{Created on 2021-11-12 by the reprex package (v2.0.1)}

Answer 2

要获得特定城市的平均值，您可以对其进行子集化并取mean 。

result <- mean(df$Age[df$CityName == 'Vancouver'], na.rm = TRUE)