I would like to know how to transform negative values to `Log()`, since I have heteroskedastic data. I read that it works with the formula `Log(x+1)` but this doesn't work with my database and I continue getting NaNs as result. E.g. I get this Warning message (I didn't put my complete database because I think with one of my negative values is enough to show an example): 

    > log(-1.27+1)
    [1] NaN
    Warning message:
    In log(-1.27 + 1) : NaNs produced
    > 

Thanks in advance