get.noise.var: Suggestion noise
In SimPhe: Tools to Simulate Phenotype(s) with Epistatic Interaction

Give suggestion on the parameter setting of noise variance according to the expected heritability.

1	get.noise.var(gene.coef, freq, heritability, Dskim = 0, ...)

`gene.coef`	a list including the coefficients of genetic effects. Each element includes 8 genetic parameters (regression coefficient) β_{Gw_{t}}, t in (1, 2, ..., 8)
`freq`	a dataframe with the allele frequencies.
`heritability`	expected heritability.
`Dskim`	the coefficient of linkage disequilibrium. Default is 0 (no LD).
`...`	not used.