R的数据结构--矩阵

m1 <- matrix(
  c(1:6),
  nrow=2,
  ncol=3,
  dimnames=list(
    c("r1","r2"),
    c("c1","c2","c3")
  )
)
"""
    c1 c2 c3
r1  1  3  5
r2  2  4  6
"""

# 共6个元素，分2行，每行3个元素，未指定行名和列名
m2 <- matrix(1:6,nrow=2)   <-->  m3 <- matrix(1:6,ncol=3)
"""
     [,1] [,2] [,3]
[1,]    1    3    5
[2,]    2    4    6
"""

#未指定元素数据，默认为NA，2行3列，nr是nrow的简写，nc是ncol的简写
m4 <- matrix(nr=2,nc=3)
""" 
        [,1] [,2] [,3]
[1,]   NA   NA   NA
[2,]   NA   NA   NA
"""

# 创建名为v1的向量
v1 <- c(1:4) 
# 创建名为v2的向量
v2 <- c(5:8) 
# 将向量v1和v2按行合并为一个矩阵
m5 <- rbind(v1,v2) 
"""
   [,1] [,2] [,3] [,4]
v1    1    2    3    4
v2    5    6    7    8
"""
# 将向量v1和v2按列合并为一个矩阵
m6 <- cbind(v1,v2) 
"""
     v1 v2
[1,]  1  5
[2,]  2  6
[3,]  3  7
[4,]  4  8
"""
# 将上面定义的矩阵m1和m2合并为一个新的矩阵
m7 <- rbind(m1,m2) 
"""
   c1 c2 c3
r1  1  3  5
r2  2  4  6
     1  3  5
     2  4  6
"""

m1
"""
   c1 c2 c3
r1  1  3  5
r2  2  4  6
"""

m1[c(1,2),c(1,3)]
"""
   c1 c3
r1  1  5
r2  2  6
"""

m1[c(1,2), ]
"""
   c1 c2 c3
r1  1  3  5
r2  2  4  6
"""

m1[ , c(1,3)]
"""
   c1 c3
r1  1  5
r2  2  6
"""

# m1矩阵行名分别为r1和r2, 列名分别为c1，c2，c3
m1 <- matrix(
  c(1:6),
  nrow=2,
  ncol=3,
  dimnames=list(
    c("r1","r2"),
    c("c1","c2","c3")
  )
)
"""
   c1 c2 c3
r1  1  3  5
r2  2  4  6
"""

m1["r1", "c2"]  # 3

m1["r2", ]
"""
c1 c2 c3 
 2  4  6 
"""

m1[ , "c1"]
"""
r1 r2 
 1  2
"""

# 除去第1行及第2列的数据
m1[-1, -2] 
"""
c1 c3 
 2  6 
"""

# 除去第2行之外的数据
m1[-2,] 
"""
c1 c2 c3 
 1  3  5 
"""

# 除去第2列之外的数据
m1[, -2] 

m1[-c(1),-c(2,3)]  # 2

m1[-c(2), ]

m1[ , -c(1:2)]