[R] t.tests by unique groupes

[Peter Dalgaard]

Imri wrote:
> Thanks for the answer, but it's still don't work.
> 
> What I get for each genotype look like this:
> 
> $`02-02`
> 
>         Welch Two Sample t-test
> 
> data:  slength[, 6] by slength[, 3] 

You can't get that if you did what I said...


> t = 1.6262, df = 682.116, p-value = 0.1044
> alternative hypothesis: true difference in means is not equal to 0 
> 95 percent confidence interval:
>  -0.1336494  1.4224993 
> sample estimates:
> mean in group d mean in group w 
>        2.419450        1.775025 
> 
>  For each of the  genotypes all the data is tests, not just the data for the
> unique genotype.
> 
>  
> 
> Peter Dalgaard wrote:
>> Imri wrote:
>>> My data (slength) look like this:
>>> Plant Block Treat Genotype Source MPH
>>> 1       1     1     w   05-AZM sp 160            NA
>>> 2       2     1     w    12-50    463            NA
>>> 3       3     1     w    12-51 sp 150     0.0508982
>>> 4       5     1     w    29-42    567     0.9017094
>>> 5       6     1     w  KNG-KNG    811            NA
>>> 6       7     1     w    02-02      1            NA
>>>
>>> Treat column has w or d for each Plant(row). I wont to do t.test of
>>> MPH~Treat for each of the genotypes (128 total). I tried :
>>>
>>> t.tests<-by(slength, slength[,4], function(x)
>>> t.test(slength[,6]~slength[,3])) 
>>>
>>> but it is not what I need.
>>> Do you have any ideas?
>>>   Thanks
>>>          Imri
>>>  
>> Your function(x)... doesn't depend on x! Try
>>
>> ...t.test(MPH~Treat, data=x)
>>
>> -- 
>>     O__  ---- Peter Dalgaard             Øster Farimagsgade 5, Entr.B
>>    c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
>>   (*) \(*) -- University of Copenhagen   Denmark      Ph:  (+45) 35327918
>> ~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)              FAX: (+45) 35327907
>>
>> ______________________________________________
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>> PLEASE do read the posting guide
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>> and provide commented, minimal, self-contained, reproducible code.
>>
>>
> 


-- 
    O__  ---- Peter Dalgaard             Øster Farimagsgade 5, Entr.B
   c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
  (*) \(*) -- University of Copenhagen   Denmark      Ph:  (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)              FAX: (+45) 35327907