R help - Jul 2008 - Sample

Hi!

I have a data.frame, like this one:
> data
  0-100 100-250 250+
a     9      18   16
b    33      25   27
c    21      19   17
d    25      22   19
e    40      39   19
f    77      45   29

If I request a sample of 2, I have the following:
> sample(data, 2)
  0-100 250+
a     9   16
b    33   27
c    21   17
d    25   19
e    40   19
f    77   29

How can I request a sample from the rows???


--
Raphael Saldanha
UFJF - Brazil
saldanha.plangeo@gmail.com


Woody Allen  - "I don't want to achieve immortality through my work. I
want
to achieve it through not dying."

	[[alternative HTML version deleted]]

like this:
> x
  0-100 100-250 250+
a     9      18   16
b    33      25   27
c    21      19   17
d    25      22   19
e    40      39   19
f    77      45   29
> x[sample(nrow(x), 3),]
  0-100 100-250 250+
e    40      39   19
c    21      19   17
a     9      18   16
> x[sample(nrow(x), 3),]
  0-100 100-250 250+
c    21      19   17
e    40      39   19
d    25      22   19
> x[sample(nrow(x), 3),]
  0-100 100-250 250+
b    33      25   27
f    77      45   29
c    21      19   17
> x[sample(nrow(x), 3),]
  0-100 100-250 250+
f    77      45   29
c    21      19   17
a     9      18   16


On Sat, Jul 26, 2008 at 5:12 PM, Raphael Saldanha
<saldanha.plangeo at gmail.com> wrote:
> Hi!
>
> I have a data.frame, like this one:
>
>> data
>  0-100 100-250 250+
> a     9      18   16
> b    33      25   27
> c    21      19   17
> d    25      22   19
> e    40      39   19
> f    77      45   29
>
> If I request a sample of 2, I have the following:
>
>> sample(data, 2)
>  0-100 250+
> a     9   16
> b    33   27
> c    21   17
> d    25   19
> e    40   19
> f    77   29
>
> How can I request a sample from the rows???
>
>
> --
> Raphael Saldanha
> UFJF - Brazil
> saldanha.plangeo at gmail.com
>
>
> Woody Allen  - "I don't want to achieve immortality through my
work. I want
> to achieve it through not dying."
>
>        [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem you are trying to solve?

On 26-Jul-08 21:12:56, Raphael Saldanha wrote:
> Hi!
> 
> I have a data.frame, like this one:
>> data
>   0-100 100-250 250+
> a     9      18   16
> b    33      25   27
> c    21      19   17
> d    25      22   19
> e    40      39   19
> f    77      45   29
> 
> If I request a sample of 2, I have the following:
> 
>> sample(data, 2)
>   0-100 250+
> a     9   16
> b    33   27
> c    21   17
> d    25   19
> e    40   19
> f    77   29
> 
> How can I request a sample from the rows???
Something like

  data[sample((1:nrow(data)),2),]

to get the samples rows in random order, or

  data[sort(sample((1:nrow(data)),2)),]

if you want just a random subset (in the original order).

(only: don't call your dataframe "data" -- that can cause
problems.
Use some other name.)

Ted.

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Date: 26-Jul-08                                       Time: 22:26:54
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