R语言 计算矩阵或数组中每一列的平均数 – colMeans()函数

R语言中的 colMeans() 函数是用来计算矩阵或数组中每一列的平均数的。

语法： colMeans(x, dims = 1)

参数：

x： 两个或多个维度的数组，包含数字、复数、整数或逻辑值，或者一个数字数据框

dims： 整数值，哪些维度被认为是要求和的 “列”。它是在维度1:dims上。

例1 :

# R program to illustrate
# colMeans function
  
# Initializing a matrix with
# 3 rows and 3 columns
x <- matrix(rep(1:9), 3, 3)
  
# Getting matrix representation
x
  
# Calling the colMeans() function
colMeans(x)

输出

     [, 1] [, 2] [, 3]
[1, ]    1    4    7
[2, ]    2    5    8
[3, ]    3    6    9

[1] 2 5 8

例2 :

# R program to illustrate
# colMeans function
  
# Initializing a 3D array
x <- array(1:12, c(2, 3, 3))
  
# Getting the array representation
x
  
# Calling the colMeans() function
  
# for dims = 1, x[, 1, 1], x[, 2, 1], x[, 3, 1],
# x[, 1, 2] ... are columns
colMeans(x, dims = 1)
  
# for dims = 2, x[,,1], x[,,2], x[,,3]
# are columns
colMeans(x, dims = 2)

输出

,, 1

     [, 1] [, 2] [, 3]
[1, ]    1    3    5
[2, ]    2    4    6,, 2

     [, 1] [, 2] [, 3]
[1, ]    7    9   11
[2, ]    8   10   12,, 3

     [, 1] [, 2] [, 3]
[1, ]    1    3    5
[2, ]    2    4    6

     [, 1] [, 2] [, 3]
[1, ]  1.5  7.5  1.5
[2, ]  3.5  9.5  3.5
[3, ]  5.5 11.5  5.5

[1] 3.5 9.5 3.5