as.snpMatrix: A snpMatrix constructor
In QTCAT/qtcat: Quantitative Trait Cluster Association Test

Constructs a snpMatrix object from the given data.

1 2	as.snpMatrix(x, chr, pos, alleleCoding = c(-1, 0, 1), allele.1 = NULL, allele.2 = NULL)

`x`	a matrix with individuals in rows and SNPs in columns.
`chr`	a vector with chromosoms at which SNPs are located.
`pos`	a vector with genomic positions at which SNPs are located.
`alleleCoding`	a coding scheme of `x` for hom (AA), het (AB), and hom (BB).
`allele.1`	labels of allele one, for each SNP.
`allele.2`	labels of allele two, for each SNP.