**170**wrote:

I am currently formatting my data for use with the GISTIC 2.0. In the documentation, it states that the Seg.CN column should be:

(log2() -1 of copy number)

I want to verify with someone who has used the software before that I should take the log of my copy numbers, and subtract one (1) to get this value.

Also, can anyone explain the significance of subtracting 1?

**90**• written 4.2 years ago by gaiusjaugustus •

**170**

Hi Etal,

What to do in case of absolute copy number 0?

Thanks

90Try a number fairly close to zero, appropriate for the accuracy/precision of the measurement -- e.g. 0.001 in absolute scale is roughly -10 in log2 scale. GISTIC should handle these values OK.

2.6kThanks Etal. What about the number of markers?

90