[R] Random Sample with Unique function

[Uwe Ligges]

You need to wrap it accordingly:

s1 <- cc[strata(cc, stratanames="ID", size=rep(1, 20), 
method="srswr")$ID_unit, ]

Uwe



Krystyna Golabek wrote:
> Thanks Uwe, 
> 
> Your strata suggestion works, thank you, but it has created a dataset of random rows but without the data, other columns involved. You see I would further like to use this random sample for a DFA (lda) analysis. Can you suggest how I would use the strata function to sample a subset of the data.frame?
> 
> Thanks
> Krystyna 
> 
>> Date: Tue, 28 Apr 2009 14:33:22 +0200
>> From: ligges at statistik.tu-dortmund.de
>> To: kagolabek at hotmail.com
>> CC: r-help at r-project.org
>> Subject: Re: [R] Random Sample with Unique function
>>
>> In order to use stratified sampling, either try to implement it yourself 
>> or use the "sampling" package and its function strata() as in:
>>
>> s1 <- strata(cc, stratanames="ID", size=rep(1, 20), method="srswr")
 >>
>> then you will get 1 observation for each ID. Note that it is not 
>> important to use "with replacement" in your case, since you only sample 
>> 1 obervation for each stratum.
>>
>> Uwe Ligges
>>
>>
>>
>>
>> Krystyna Golabek wrote:
>>> Dear R-users
>>>
>>> I have a dataset of 243 lines with replicate information for 20 different individuals (ID). 
>>> I would like to randomly sample this dataset 100 times with a selection of unique IDs in each sample.
>>>
>>> First to create a random sample I have;
>>>
>>> cc<-read.table(blah.blah.blah)
>>> names(cc)
>>>  [1] "CALL"        "CONTEXT"     "ORDER"       "ID"          "STATUS"     
>>>
>>> s1<-cc[sample(1:243,20,replace=TRUE),]
>>>
>>> This code samples 20 rows from the dataset but can anyone help me write the code to request unique(ID) in this sample?
>>>
>>> Thank you so much for your time and help.
>>>
>>> Krystyna Golabek
>>>
>>>
>>>
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