例如我们根据某个分组，计算他的多个分位数

  1. > library(dplyr)
  2. > library(tidyr)
  3. > 
  4. > Z <- data.frame(x = runif(1000, min = 0, max = 20)) %>%
  5. +     mutate(y = rnorm(n(), mean = sin(x))) %>%
  6. +     group_by(x.category = round(x)) 
  7. > Z
  8. # A tibble: 1,000 x 3
  9. # Groups:   x.category [21]
  10.         x       y x.category
  11.     <dbl>   <dbl>      <dbl>
  12.  1  0.670  0.121           1
  13.  2 16.5    0.0702         16
  14.  3 15.0   -1.47           15
  15.  4  3.16  -0.595           3
  16.  5 12.7   -0.915          13
  17.  6  5.25  -0.540           5
  18.  7  3.82  -0.671           4
  19.  8 10.6   -2.33           11
  20.  9 18.3    1.15           18
  21. 10  1.53   0.205           2
  22. # … with 990 more rows
  25. Z %>%
  26.   summarize(x = mean(x),
  27.             y25 = quantile(y, probs = .25),
  28.             y50 = quantile(y, probs = .5),
  29.             y75 = quantile(y, probs = .75)) %>%
  30.   gather(Statistic, y, -x, -x.category)
  31. #上述是比较繁琐的方法，如果有多个分位数可能就要写很多次。
  32. #那么如何一次性生成多列呢

解法一

  1. probs <- c(0.25, 0.5, 0.75)
  2. Z %>%
  3.   summarize(x = mean(x),
  4.             quantile = list(quantile(y,probs)),
  5.             prob = list(probs)) %>% 
  6.   unnest(cols = c("quantile", "prob"))
  7. # A tibble: 63 x 4
  8. #    x.category     x quantile  prob
  9. #         <dbl> <dbl>    <dbl> <dbl>
  10. #  1          0 0.260   -0.527  0.25
  11. #  2          0 0.260    0.247  0.5 
  12. #  3          0 0.260    0.704  0.75
  13. #  4          1 0.997    0.449  0.25
  14. #  5          1 0.997    0.912  0.5 
  15. #  6          1 0.997    1.61   0.75
  16. #  7          2 2.00    -0.219  0.25
  17. #  8          2 2.00     0.531  0.5 
  18. #  9          2 2.00     1.48   0.75
  19. # 10          3 2.93    -0.498  0.25
  20. # ... with 53 more rows

解法二

  1. q = c(0.25, 0.5, 0.75)
  2. Z %>%
  3.      summarise(x = mean(x),
  4.                qtls = paste(quantile(y, q), collapse = ","))  %>%
  5.      separate(qtls, paste0("y_", 100*q), sep = ",", convert = T)