R:如何获取每n行的最小值和最大值或其他函数 [英] R: How to take the min and max or other functions of every n rows

问题描述

我有一个数据框，我将一个变量放入向量中.

I have a dataframe of which I put one variable into a vector.

从这个向量中，我想为每5个值计算mean，min和max值.

From this vector, I would like to calculate for every 5 values mean, min and max value.

我设法通过这种方式计算出平均值:

I have managed to calculate the means in this way:

means <- colMeans(matrix(df$values, nrow=5))

我知道我可以这样计算最小值和最大值:

I know I can calculate the min and max like this:

max <- max(df$values[1:5])
min <- min(df$values[1:5])

如何为每个五个值重复此操作?

How do I repeat this for every five values?

另外，如何从每个n行的1样本t检验中获得统计量和p值?

Aditionally, how can I get statistic and p-value from a 1-sample t-test for each n-row?

推荐答案

您可以为此使用sapply和split:

sapply(split(df$value, rep(1:(nrow(df)/5), each=5)), mean)
sapply(split(df$value, rep(1:(nrow(df)/5), each=5)), min)
sapply(split(df$value, rep(1:(nrow(df)/5), each=5)), max)

如果您希望以矩阵形式输出，则可以使用

If you want the outputs in a matrix you can use what @lmo proposed in the comments:

sapply(split(df$value, rep(1:(nrow(df)/5), each=5)),
                       function(x) c(mean=mean(x), min=min(x), max=max(x)))

更新

如何从每个n行的样本t检验中获取统计量和p值: 这将很难实施.看下面;

Update

How to get statistic and p-value from a sample t-test for each n-row: This would be a bit harder to implement. Look below;

#mu=3 for sample t-test
t_test_list <- sapply(split(df$value, rep(1:(nrow(df)/5), each=5)), t.test, mu=3) 

p_value_list <- lapply(as.data.frame(t_test_list),function(x) x$p.value)
statistic_list <- lapply(as.data.frame(t_test_list),function(x) x$statistic)

每5行

p_value_list和statistic_list分别是p.value和statistic.

p_value_list and statistic_list are p.value and statistic for each 5 rows.

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