A question about purity assumption in the Docs

[RysBen]

Hi there,

I read this in part Calling methods of the document:

But the outer cutoffs of -1.1 and +0.7 assume 100% purity, ...

However, My calculations using the formula log2( (1 - purity) + purity * (0:4) / ploidy ) are as follows:

copy numbers	purity=0.2	purity=0.5	purity=1
0 (del)	-0.32-0.1	-1.0-0.1	-Inf
1 (loss)	-0.15-0.1	-0.4-0.1	-1.0-0.1
2 (neutral)	0.0	0.0	0
3 (gain)	0.13+0.1	0.3+0.1	0.6+0.1
4 (amp)	0.26+0.1	0.6+0.1	1.0+0.1

Note: 0.1 is allowed for random noise according the code.

It looks like the purity assumption of outer cutoffs should be 50%, not 100%.

Could you point out where my understanding is wrong?

Thanks