如果你想比较两组的平均值,在我看来 t 检验是一个不错的选择。这是使用tidyverse的选项。首先,我创建了一个名为dat
.
# Load package
library(tidyverse)
# Set seed
set.seed(12345)
# Create example data frame
dat <- expand.grid(class1 = 1:5, class2 = 1:5) %>%
slice(rep(1:n(), 5)) %>%
mutate(rev1 = rnorm(n()), rev2 = rnorm(n())) %>%
mutate(rev2 = sample(rev2, size = n(), replace = TRUE))
# View the head of data frame
dat
# # A tibble: 125 x 4
# class1 class2 rev1 rev2
# <int> <int> <dbl> <dbl>
# 1 1 1 0.586 0.548
# 2 2 1 0.709 0.868
# 3 3 1 -0.109 0.0784
# 4 4 1 -0.453 -0.567
# 5 5 1 0.606 -0.0767
# 6 1 2 -1.82 0.167
# 7 2 2 0.630 2.66
# 8 3 2 -0.276 0.831
# 9 4 2 -0.284 -1.70
# 10 5 2 -0.919 -2.13
# # ... with 115 more rows
之后,我在class1
==时过滤了数据框class2
,将数据按 分组class1
,然后使用该do
函数进行 t 检验。最后,map_dbl
可以得到每个 t.test 的 p.value 到一个新的数据框。
dat2 <- dat %>%
filter(class1 == class2) %>%
group_by(class1) %>%
do(data_frame(class = .$class1[1],
TTest = list(t.test(.$rev1, .$rev2)))) %>%
mutate(PValue = map_dbl(TTest, "p.value"))
dat2
# # A tibble: 5 x 4
# # Groups: class1 [5]
# class1 class TTest PValue
# <int> <int> <list> <dbl>
# 1 1 1 <S3: htest> 0.700
# 2 2 2 <S3: htest> 0.381
# 3 3 3 <S3: htest> 0.859
# 4 4 4 <S3: htest> 0.0580
# 5 5 5 <S3: htest> 0.206
如果要访问特定类的测试结果,可以执行以下操作。
# Get the result of the first class
dat2$TTest[dat2$class == 1]
# [[1]]
#
# Welch Two Sample t-test
#
# data: .$rev1 and .$rev2
# t = 0.40118, df = 7.3956, p-value = 0.6996
# alternative hypothesis: true difference in means is not equal to 0
# 95 percent confidence interval:
# -0.9379329 1.3262368
# sample estimates:
# mean of x mean of y
# 0.6033533 0.4092013
这是另一种选择,我们还可以将数据框拆分为列表并通过列表应用 t 检验。
# Split the data frame and conduct T-test
dat_list <- dat %>%
filter(class1 == class2) %>%
split(.$class1) %>%
map(~t.test(.$rev1, .$rev2))
# Get the result of the first class
dat_list$`1`
# Welch Two Sample t-test
#
# data: .$rev1 and .$rev2
# t = 0.40118, df = 7.3956, p-value = 0.6996
# alternative hypothesis: true difference in means is not equal to 0
# 95 percent confidence interval:
# -0.9379329 1.3262368
# sample estimates:
# mean of x mean of y
# 0.6033533 0.4092013