dplyr创建因子水平的总计百分比 [英] dplyr to create aggregate percentages of factor levels
问题描述
如何使用dplyr为每个州创建因子变量水平的比例?例如,我想添加一个变量来指示数据框内每个州内女性的百分比。
How do I use dplyr to create proportions of a level of a factor variable for each state? For example, I'd like to add a variable that indicates the percent of females within each state to the data frame.
# gen data
state <- rep(c(rep("Idaho", 10), rep("Maine", 10)), 2)
student.id <- sample(1:1000,8,replace=T)
gender <- rep( c("Male","Female"), 100*c(0.25,0.75) )
gender <- sample(gender, 40)
school.data <- data.frame(student.id, state, gender)
这是我知道是错误的尝试,但可以让我访问以下信息:
Here's an attempt that I know is wrong, but gets me access to the information:
middle %>%
group_by(state, gender %in%c("Female")) %>%
summarise(count = n()) %>%
mutate(test_count = count)
我很难使用count和mutate函数,因此很难进一步了解。它的行为不符合我的预期。
I have a hard time with the count and mutate functions, which makes it hard to get much further. It doesn't behave as I'd expect.
推荐答案
要在现有数据框中添加新列:
To add a new column to your existing data frame:
school.data %>%
group_by(state) %>%
mutate(pct.female = mean(gender == "Female"))
使用总结
而不是变异
,如果您只希望每个状态一行而不是在原始数据中添加一列。
Use summarize
rather than mutate
if you just want one row per state rather than adding a column to the original data.
school.data %>%
group_by(state) %>%
summarize(pct.female = mean(gender == "Female"))
# # A tibble: 2 x 2
# state pct.female
# <fctr> <dbl>
# 1 Idaho 0.75
# 2 Maine 0.70
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