xtable的每列data.table或data.frame的摘要

Question

我想使用data.table或data.frame的每一列的摘要用于sweave包xtable。这是MWE。

summary(iris)
  Sepal.Length    Sepal.Width     Petal.Length    Petal.Width          Species  
 Min.   :4.300   Min.   :2.000   Min.   :1.000   Min.   :0.100   setosa    :50  
 1st Qu.:5.100   1st Qu.:2.800   1st Qu.:1.600   1st Qu.:0.300   versicolor:50  
 Median :5.800   Median :3.000   Median :4.350   Median :1.300   virginica :50  
 Mean   :5.843   Mean   :3.057   Mean   :3.758   Mean   :1.199                  
 3rd Qu.:6.400   3rd Qu.:3.300   3rd Qu.:5.100   3rd Qu.:1.800                  
 Max.   :7.900   Max.   :4.400   Max.   :6.900   Max.   :2.500                  

library(xtable)

lapply(iris, summary)
$Sepal.Length
   Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
  4.300   5.100   5.800   5.843   6.400   7.900 

$Sepal.Width
   Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
  2.000   2.800   3.000   3.057   3.300   4.400 

$Petal.Length
   Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
  1.000   1.600   4.350   3.758   5.100   6.900 

$Petal.Width
   Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
  0.100   0.300   1.300   1.199   1.800   2.500 

$Species
    setosa versicolor  virginica 
        50         50         50 
xtableList(lapply(iris, summary))
Error in xtable.table(x[[i]], caption = caption, label = label, align = align,  : 
  xtable.table is not implemented for tables of > 2 dimensions

想知道如何在单独的表格中获取每列的摘要，以用于sweave或knitr。提前谢谢。