R:保留1行/列矩阵[重复]

我猜是被改写了 F ; f 可以设置为变量,在这种情况下不再为false。总是写出来 FALSE 完全不能设置为变量。

见 Is there anything wrong with using T & F instead of TRUE & FALSE?

也 R Inferno 第8.1.32节是一个很好的参考。

> F <- 1
> test = matrix(letters[1:5]) # is a matrix
> test[5:1,,drop=F]           # not a matrix
[1] "e" "d" "c" "b" "a"
> test[5:1,,drop=FALSE]       # but this is a matrix
     [,1]
[1,] "e" 
[2,] "d" 
[3,] "c" 
[4,] "b" 
[5,] "a" 
> rm(F)
> test[5:1,,drop=F]           # now a matrix again
     [,1]
[1,] "e" 
[2,] "d" 
[3,] "c" 
[4,] "b" 
[5,] "a" 

你问题中的代码在新的R会话中运行良好:

test = matrix(letters[1:5]) # is a matrix
result = test[5:1,,drop=F]  
result
#      [,1]
# [1,] "e" 
# [2,] "d" 
# [3,] "c" 
# [4,] "b" 
# [5,] "a" 
class(result)  # still a matrix
# [1] "matrix"
dim(result)
# [1] 5 1

即使在1x1矩阵上:

test3 = matrix(1)  # is a matrix
result3 = test3[1:1,,drop=F]
class(result3)
# [1] "matrix"
dim(result3)
# [1] 1 1

也许您已经加载了其他覆盖默认行为的包?是什么让你认为你没有一个矩阵?

以下工作:

test <- matrix(test[5:1,, drop = F], nrow = 5, ncol = 1)

当你使用 is.matrix 为了测试它,输出是一个矩阵。同时,指定行数( nrow )以及列数( ncol )将其强制为所需的行数和列数。