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Question

我遇到了一个应用程序,我需要按列号对data.frame进行排序,而且通常的解决方案似乎都不允许这样做.

上下文正在创建一个as.data.frame.by方法.由于by对象将其最后一列作为值列,而将第一列ncol-1列作为索引列. melt返回它向后排序 - 索引3,然后索引2,然后索引1.为了兼容latex.table.by我想要向前排序.但是我在以足够通用的方式做这件事时遇到了麻烦.下面函数中注释掉的行是迄今为止我最好的尝试.

as.data.frame.by <- function( x, colnames=paste("IDX",seq(length(dim(x))),sep="" ), ... ) {
  num.by.vars <- length(dim(x))
    res <- melt(unclass(x))
  res <- na.omit(res)
    colnames(res)[seq(num.by.vars)] <- colnames
    #res <- res[ order(res[ , seq(num.by.vars)] ) , ] # Sort the results by the by vars in the heirarchy given
    res
}

dat <- transform( ChickWeight, Time=cut(Time,3), Chick=cut(as.numeric(Chick),3) )
my.by <- by( dat, with(dat,list(Time,Chick,Diet)), function(x) sum(x$weight) )
> as.data.frame(my.by)
            IDX1         IDX2 IDX3 value
1  (-0.021,6.99] (0.951,17.3]    1  3475
2      (6.99,14] (0.951,17.3]    1  5969
3        (14,21] (0.951,17.3]    1  8002
4  (-0.021,6.99]  (17.3,33.7]    1   640
5      (6.99,14]  (17.3,33.7]    1  1596
6        (14,21]  (17.3,33.7]    1  2900
13 (-0.021,6.99]  (17.3,33.7]    2  2253
14     (6.99,14]  (17.3,33.7]    2  4734
15       (14,21]  (17.3,33.7]    2  7727
22 (-0.021,6.99]  (17.3,33.7]    3   666
23     (6.99,14]  (17.3,33.7]    3  1391
24       (14,21]  (17.3,33.7]    3  2109
25 (-0.021,6.99]    (33.7,50]    3  1647
26     (6.99,14]    (33.7,50]    3  3853
27       (14,21]    (33.7,50]    3  7488
34 (-0.021,6.99]    (33.7,50]    4  2412
35     (6.99,14]    (33.7,50]    4  5448
36       (14,21]    (33.7,50]    4  8101

如果该行未被注释,它将返回乱码(它只是将整个data.frame视为一个向量,带来灾难性的结果).

我甚至尝试过聪明的东西,res <- res[ order( ...=list(res[,1],res[,2]) ) , ]但无济于事.

我怀疑有一种简单的方法可以做到这一点,但我没有看到它.

编辑以澄清:我不想指定列名.相反,我希望能够通过数字向量对其进行排序(例如,按列1:4排序).

Answer 1

mydf <- as.data.frame(my.by)
mydf[order(mydf$IDX3, mydf$IDX2, mydf$IDX1) , ]
            IDX1         IDX2 IDX3 value
1  (-0.021,6.99] (0.951,17.3]    1  3475
3        (14,21] (0.951,17.3]    1  8002
2      (6.99,14] (0.951,17.3]    1  5969
4  (-0.021,6.99]  (17.3,33.7]    1   640
6        (14,21]  (17.3,33.7]    1  2900
5      (6.99,14]  (17.3,33.7]    1  1596
13 (-0.021,6.99]  (17.3,33.7]    2  2253
15       (14,21]  (17.3,33.7]    2  7727
14     (6.99,14]  (17.3,33.7]    2  4734
22 (-0.021,6.99]  (17.3,33.7]    3   666
24       (14,21]  (17.3,33.7]    3  2109
23     (6.99,14]  (17.3,33.7]    3  1391
25 (-0.021,6.99]    (33.7,50]    3  1647
27       (14,21]    (33.7,50]    3  7488
26     (6.99,14]    (33.7,50]    3  3853
34 (-0.021,6.99]    (33.7,50]    4  2412
36       (14,21]    (33.7,50]    4  8101
35     (6.99,14]    (33.7,50]    4  5448

要么 ;

my.by <- by( dat, with(dat,list(Diet,Chick, Time)), function(x) sum(x$weight) )
mydf <- as.data.frame(my.by)

编辑:或者使用数字列索引生成与顶部相同的输出:

 mydf <- as.data.frame(my.by)
 mydf[ do.call(order, mydf[, 3:1] ) , ]