每个人的观察次数中位数

Question

我有一个长格式的数据框，显示一组人的身高重复测量值。

观察的平均数计算为 2000/500 = 每个 child.

4 个观察

如何计算每个 child 的观测值数量的中值和四分位距？

data <- data.frame(

child_id = 1:500,
height_1 = rnorm(500, mean = 80, sd = 2),
height_2 = rnorm(500, mean = 90, sd = 2),
height_3 = rnorm(500, mean = 100, sd = 2),
height_4 = rnorm(500, mean = 115, sd = 2)
)

data_long <- reshape(data, varying=c(
"height_1", "height_2", "height_3", "height_4"),
direction= "long", idvar="child_id", timevar = "time", sep="_"
)

# Mean observation per child = 2000/500 = 4
data_long$id_f <- as.factor(data_long$child_id)
length(unique(data_long$id_f)) # 500 children

length(data_long$height) # 2000 observations

Answer 1

我们可以使用dplyr。按'child_id'分组，得到'height'列的median和IQR

library(dplyr)
data_long %>% 
   group_by(child_id) %>%
   summarise(median = median(height),
            interQuartileRange = IQR(height))

如果我们想要median和IQR基于观测值

data_long %>%
  count(child_id) %>% 
  summarise(median = median(n), IQR = IQR(n))

每个人的观察次数中位数

Median number of observations per person

r

dplyr

data-manipulation

longitudinal