[R] convert list to numeric

[Adaikalavan Ramasamy]

It's a way of extracting from a list. See help("[") or help("Extract").



dadrivr wrote:
> Great, that works very well.  What is the purpose of double brackets vs
> single ones?  I will remember next time to include a subset of the data, so
> that readers can run the script.  Thanks again for your help!
>  
> 
> Benilton Carvalho wrote:
>> it appears that what you really want is to use:
>>
>> task[[i]]
>>
>> instead of task[i]
>>
>> b
>>
>> On Nov 1, 2009, at 11:04 PM, dadrivr wrote:
>>
>>> I would like to preface this by saying that I am new to R, so I  
>>> would ask
>>> that you be patient and thorough, so that I'm not completely  
>>> clueless.  I am
>>> trying to convert a list to numeric so that I can perform  
>>> computations on it
>>> (specifically mean-center the variable), but I am running into  
>>> problems.  I
>>> have imported the data set into "task" (data frame).  The data frame  
>>> is made
>>> of factors with variable names in the first row.  I am running a  
>>> loop to set
>>> a variable equal to a column in the data frame.  Here is an example  
>>> of my
>>> problem:
>>>
>>> for (i in 1:dim(task)[2]){
>>> predictor.loop <- c(task[i])
>>> predictor.loop.mc <- predictor.loop - mean(predictor.loop, na.rm=T)
>>> }
>>>
>>> I get the following error:
>>> Error in predictor.loop - mean(predictor.loop, na.rm = T) :
>>>  non-numeric argument to binary operator
>>> In addition: Warning message:
>>> In mean.default(predictor.loop, na.rm = T) :
>>>  argument is not numeric or logical: returning NA
>>>
>>> The column is entirely made up of numerical data, except for the  
>>> header,
>>> which is a string.  My problem is that I receive an error because the
>>> predictor.loop variable is not numerical, so I need to find a way to  
>>> convert
>>> it.  I tried using:
>>> predictor.loop <- c(as.numeric(task[i]))
>>> But I get the following error: "Error: (list) object cannot be  
>>> coerced to
>>> type 'double'"
>>>
>>> If I call the variable, I can assign it to a numerical list (e.g.,  
>>> predictor
>>> loop <- task$variablename), but since I am assigning the variable in  
>>> a loop,
>>> I have to find another way as the variable name would have to change  
>>> in each
>>> loop iteration.  Any help would be greatly appreciated.  Thanks!
>>> --
>>> View this message in context:
>>> http://old.nabble.com/convert-list-to-numeric-tp26155039p26155039.html
>>> Sent from the R help mailing list archive at Nabble.com.
>>>
>>> ______________________________________________
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>>> PLEASE do read the posting guide
>>> http://www.R-project.org/posting-guide.html
>>> and provide commented, minimal, self-contained, reproducible code.
>> ______________________________________________
>> 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.
>>
>>
>