[R] convert list to numeric

[Benilton Carvalho]

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!
> --
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