R help - Sep 2010 - next step in randomly sampling

Thanks to the people on this list I was able to fix my code for randomly
sampling.  Thanks.  

 

Now, I am moving on to the next step and I ran into another snag.  I have a
large dataset but I am starting with a small made-up dataset until I figure
it out.  I have two columns of data (age and length).  I got R to read my
data called growth which is the age and length for 10 fish:  

 
> growth
  Age Length

1   2    200

2   5    450

3   6    600

4   7    702

5   8    798

6   5    453

7   4    399

8   1    120

9   2    202

 

Then I believe I converted my data to a three vectors by: 

 

newgrowth<-c(growth)

 

Now I want to randomly select the values from this dataset to create a new
dataset.  I want to do this many times, however, for now I am just trying to
get it to randomly select from the dataset only once.  The trick is that I
need to keep the columns together.  Each age corresponds to a length.  For
example, the 200 length fish has an age of 2 years.  

 

I tried to resample the data with this code:   

 

sample(newgrowth)

 

However, I ended up getting the data listed as a row in the same order, not
randomly selected.  I pasted the result below.  

 
> sample(newgrowth)
$Age

[1] 2 5 6 7 8 5 4 1 2

 

$Length

[1] 200 450 600 702 798 453 399 120 202

 

Any advice on how I can randomly select from these 9 rows of data would be
greatly appreciated.  

 

Mike


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Mike,

Try

growth[sample(1:length(growth)),]

to permute the rows.

Jonathan


On Tue, Sep 28, 2010 at 8:38 PM, Michael Larkin
<mlarkin@rsmas.miami.edu>wrote:
> Thanks to the people on this list I was able to fix my code for randomly
> sampling.  Thanks.
>
>
>
> Now, I am moving on to the next step and I ran into another snag.  I have a
> large dataset but I am starting with a small made-up dataset until I figure
> it out.  I have two columns of data (age and length).  I got R to read my
> data called growth which is the age and length for 10 fish:
>
>
>
> > growth
>
>  Age Length
>
> 1   2    200
>
> 2   5    450
>
> 3   6    600
>
> 4   7    702
>
> 5   8    798
>
> 6   5    453
>
> 7   4    399
>
> 8   1    120
>
> 9   2    202
>
>
>
> Then I believe I converted my data to a three vectors by:
>
>
>
> newgrowth<-c(growth)
>
>
>
> Now I want to randomly select the values from this dataset to create a new
> dataset.  I want to do this many times, however, for now I am just trying
> to
> get it to randomly select from the dataset only once.  The trick is that I
> need to keep the columns together.  Each age corresponds to a length.  For
> example, the 200 length fish has an age of 2 years.
>
>
>
> I tried to resample the data with this code:
>
>
>
> sample(newgrowth)
>
>
>
> However, I ended up getting the data listed as a row in the same order, not
> randomly selected.  I pasted the result below.
>
>
>
> > sample(newgrowth)
>
> $Age
>
> [1] 2 5 6 7 8 5 4 1 2
>
>
>
> $Length
>
> [1] 200 450 600 702 798 453 399 120 202
>
>
>
> Any advice on how I can randomly select from these 9 rows of data would be
> greatly appreciated.
>
>
>
> Mike
>
>
>        [[alternative HTML version deleted]]
>
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>
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