[R] Convert factor to "double"?

[p.silva at gmx.net]

> 
> > Anyway, I would like to Fourier-transform one column. So I say:
> >> fft(test1$vP)
> > Error in levels(x)[x] : invalid subscript type 'complex'

> >> test1$vP[1:10]
> >  [1] 110 108 116 118 114 120 117 111 95  118
> > 166 Levels: - 0 1 10 100 101 102 103 104 105 106 107 108 109 11 110 111
> ... 99
> 
> 
> Obviously there is some "-" sign in your data file. You might want to 
> fix that prior to importing the data. You cannot convert easily to 
> numeric with artifacts like the string "-" in your data.
> 
> Uwe Ligges

Thanks a lot! This works now!

Philip Silva
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