Questions about ploidy estimate

[ysbioinfo]

Hi FACETS developers,
When I use FACETS on my WES data, I realized that the ploidy estimate (fit$ploidy) can be much different from the CN segment profile. Below I attached an example:

As you can see, most large segments lie on CN2 or CN3 horizontal lines, but the ploidy given by FACETS is 5.14 (purity = 0.38). I just want to make sure this is not a bug. Maybe ploidy is inferred independent of absolute copy number, am I right?

If that is true, which one should I use as the "mean ploidy"?

1. The value from fit$ploidy
2. The mean value of absolute CNs of all segments, weighted by the segment length

Do you have any recommendation? Thanks in advance!

Best
Yang