Hi everybody,

I would be very grateful if you could give me your thoughts on the following issue. 

I need to perform  Box-Cox (bcPower) transformation on my data. To do this, I calculated lambda using the function 'powerTransform'. 
  powerTransform(data)
However, I got an error message when performing this function:
  Convergence failure: return code = 52 
I was told by John Fox that the nature of my data was probably causing the problem so I applied the following transformation:
  powerTransform(1e7*(data - 0.99*(min(data))))   [1]
And it worked! However, now when I try to check the normality of my data,  
  shapiro.test(data) 
I get a new warning message:
  Error in shapiro.test(data) : 
    ifault=6. This should not happen
I think this may be solved by removing the transformation I applied previously in [1], but I’m not sure how to do it properly.

Could anyone give me some advice? 

MY DATA:
c(0.000103113, 0.000102948, 0.000104001, 0.000103794, 0.000104628, 
9.2765e-05, 9.4296e-05, 9.5025e-05, 9.4978e-05, 9.8821e-05, 9.7586e-05, 
9.6285e-05, 0.00010158, 0.000100919, 0.000103535, 0.000103321, 
0.000102842, 0.000102315, 0.0001033, 0.000103691, 0.000102689, 
0.000103248, 0.000101216, 0.000103127, 0.000103439, 0.000102818, 
0.000103482, 0.00010227, 0.000104264, 0.000104672, 0.000104586, 
0.000104516, 0.000104585, 0.000103804, 0.000103702, 0.000103405, 
0.000104815, 0.000101718, 0.000101792, 0.000103273, 0.000102942, 
0.000102522, 0.000103149, 0.0001036995, 0.0001039735, 0.000101487666666667, 
0.000102796)

Thanks a lot!!

Bea




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