[R] column selection in list

[Ivan Calandra]

Thanks, I didn't think about the help for such a character.
Ivan

Le 1/22/2010 18:50, baptiste auguie a écrit :
> ?"[" should give you enough information. In short, "[" is an operator
> to extract elements, you can think of it as a function with special
> semantics. For a simple vector,
>
> v = c("one", "two")
>
> v[2] selects the second element of the vector, and is equivalent to,
>
> `[`(v, 2)
> # "two"
>
> as you can see from,
>
> call("[",v,2)
> # c("one", "two")[2]
>
>
> So, in lapply(), I specified "[" as the function to be applied to each
> element of the list, and I passed an additional parameter indicating
> which object should be selected ("y").
>
> Best,
>
> baptiste
>
>
> 2010/1/22 Ivan Calandra<ivan.calandra at uni-hamburg.de>:
>    
>> Thanks Baptiste, it does help.
>>
>> However, I don't really understand what "[" means. Could you please tell me
>> more about it? I didn't find anything helpful on that in the help.
>>
>> Thanks in advance
>> Ivan
>>
>>
>>
>> Le 1/22/2010 17:19, baptiste auguie a écrit :
>>      
>>> Hi,
>>>
>>> Try this,
>>>
>>> a = replicate(3, data.frame(x=1:10, y=rnorm(10)), simplify=FALSE)
>>>
>>> lapply(a, "[", "y")
>>>
>>> HTH,
>>>
>>> baptiste
>>>
>>> 2010/1/22 Ivan Calandra<ivan.calandra at uni-hamburg.de>:
>>>
>>>        
>>>> Hi everybody!
>>>>
>>>> I have a (stupid) question but I cannot find a way to do it!
>>>>
>>>> I have a list like:
>>>>
>>>>          
>>>>> SPECSHOR_tx_Asfc
>>>>>
>>>>>            
>>>> $cotau
>>>>    SPECSHOR Asfc.median
>>>> 38    cotau    381.0247
>>>> 39    cotau    154.6280
>>>> 40    cotau    303.3219
>>>> 41    cotau    351.2933
>>>> 42    cotau    156.5327
>>>> $eqgre
>>>>     SPECSHOR Asfc.median
>>>> 145    eqgre    219.5389
>>>> 146    eqgre    162.5926
>>>> 147    eqgre    146.3726
>>>> 148    eqgre    127.6413
>>>> 149    eqgre    274.2888
>>>> $gicam
>>>>     SPECSHOR Asfc.median
>>>> 263    gicam    174.7445
>>>> 264    gicam     83.4821
>>>> 265    gicam    157.6005
>>>> 266    gicam    153.7519
>>>> 267    gicam    344.9775
>>>>
>>>> I would just like to remove the column "SPECSHOR" (or extract the other
>>>> one)
>>>> so that it looks like
>>>> $cotau
>>>>     Asfc.median
>>>> 38        381.0247
>>>> 39       154.6280
>>>> 40        303.3219
>>>> 41        351.2933
>>>> 42        156.5327
>>>> etc.
>>>>
>>>> How should I do it? I know how to select each element like
>>>> SPECSHOR_tx_Asfc[[1]], but I don't know how to select a single column
>>>> within
>>>> an element.
>>>>
>>>> Could you please help me on that?
>>>>
>>>> Thanks
>>>> Ivan
>>>>
>>>> ______________________________________________
>>>> 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.
>>>>
>>>>
>>>>          
>>>
>>>        
>> --
>> Ivan CALANDRA
>> PhD Student
>> University of Hamburg
>> Biozentrum Grindel und Zoologisches Institut und Museum
>> Martin-Luther-King-Platz 3
>> D-20146 Hamburg, GERMANY
>> +49(0)40 42838 6231
>> ivan.calandra at uni-hamburg.de
>>
>>
>> **********
>> http://www.for771.uni-bonn.de
>> http://webapp5.rrz.uni-hamburg.de/mammals/eng/mitarbeiter.php
>>
>>
>>      
>