相关疑难解决方法(0)

当我将矩阵子集化为单个列时,结果是类数字,而不是矩阵(即myMatrix [,5]到第五列的子集).是否有一种紧凑的方法可以将单个列子集化,维护矩阵格式,并维护行/列名称,而无需执行以下操作:

matrix( myMatrix[ , 5 ] , dimnames = list( rownames( myMatrix ) , colnames( myMatrix )[ 5 ] )

似乎在访问具有1列的表时,访问的操作会抛弃列信息.如果有超过1列,则保留此信息.

例如

表中有1个项目:

> example1 <- data.frame( items = c("A","B","B","C","C","C","C")
+                       , time = ISOdate(2222,1,1) )
> table1 <- table(example1)
> table1
     time
items 2222-01-01 12:00:00
    A                   1
    B                   2
    C                   4

> barplot(table1, legend=T)
> table1.ordered <- table1[c(3,2,1),]   # reorder
> table1.ordered
C B A 
4 2 1 
> barplot(table1.ordered, legend=T) # time column thrown away

现在表中有2个项目 :( 在此示例中添加到example1)

> example2 <- rbind(example1 , data.frame(items = NA, time = ISOdate(3333,1,1)) )
> example2
  items                time
1 …

R几乎每天都一次又一次地让我感到惊讶:

m <- matrix( 1:6, ncol=2 )
while( dim(m)[1] > 0 ){
  print(m);
  m <- m[-1,]
}

得到:

     [,1] [,2]
[1,]    1    4
[2,]    2    5
[3,]    3    6
     [,1] [,2]
[1,]    2    5
[2,]    3    6
Error in while (dim(m)[1] > 0) { : argument is of length zero

R有1xn矩阵的问题或我的错误在哪里？

> nrow( m[-c(2,3), ] )
NULL
> dim( m[-c(2,3), ] )
NULL
> m[-c(2,3), ][,1]
Error in m[-c(2, 3), ][, 1] : incorrect number of dimensions
> str( m[-c(2,3), …