Transforming results of the summary function

Hi all,

I have a question about transforming the data from summary function.
Let's say I have a data frame like this:

x = data.frame(a = c(rep("lev1", 5), rep("lev2", 5)), b = c(rnorm(5)+2, rnorm(5)))
x

a          b
1  lev1  1.5964765
2  lev1  2.2945609
3  lev1  3.5285787
4  lev1  1.4439838
5  lev1  2.2948826
6  lev2  1.7063506
7  lev2 -0.4042742
8  lev2 -1.6485337
9  lev2 -1.1163817
10 lev2 -0.2023246

I'd like to create quantiles for every level of the "a" column. Looking
into the documentation, I found the function "by" with which I can
perform the calculations...

xs = by(x, x$a, function(x) summary(x$b))
xs

x$a: lev1
   Min. 1st Qu.  Median    Mean 3rd Qu.    Max.
  1.444   1.596   2.295   2.232   2.295   3.529
------------------------------------------------------------
x$a: lev2
   Min. 1st Qu.  Median    Mean 3rd Qu.    Max.
-1.6490 -1.1160 -0.4043 -0.3330 -0.2023  1.7060

...but I need them saved as a CSV file, so I'd like the result to have the form of:

level    Min. 1st Qu.  Median    Mean 3rd Qu.    Max.
 lev1   1.444   1.596   2.295   2.232   2.295   3.529
 lev2  -1.6490 -1.1160 -0.4043 -0.3330 -0.2023  1.7060

Can you give me any hints?

Regards,
Maciej

Maciej Blizi??ski <m.blizinski at wit.edu.pl>
http://automaciej.blogspot.com/