Question

我需要对以下数据进行两步分析：

1 5 1 -2
2 6 3 4
1 5 4 -3
NA NA NA NA
2 5 4 -4

步骤1.删除所有NA行（这些行总是整行，而不是单元格）步骤2.按第4列的值按降序对行进行排序

结果应如下：

如何在考虑数据集可能很大（例如100,000个条目）的情况下，如何有效地执行此处理。

Answer 1

另一种方法是首先删除所有NA值，然后对矩阵进行排序。

# make a matrix
my_mat <- matrix(c(1,2,1,1,2,5,6,5,2,5,1,3,4,2,4,-2,4,-3,2,-4),
             nrow = 5, ncol = 4)

# add some NA values
my_mat[4,] <- NA

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


# remove rows that contain any number of NAs, for this purpose
# NAs always occupy the entire row as specified in the question
my_mat <- my_mat[complete.cases(my_mat),]

# order by the 4th column
my_mat[order(my_mat[,4], decreasing = TRUE),]

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

删除NA并按列的值对行进行排序

1 个答案: