Extract ranges of genes, and map ranges to corresponding genes

grangesToSymbol

geneRanges <- 
    function(db, column="ENTREZID")
{
    g <- genes(db, columns=column)
    col <- mcols(g)[[column]]
    genes <- granges(g)[rep(seq_along(g), elementNROWS(col))]
    mcols(genes)[[column]] <- as.character(unlist(col))
    genes
}

splitColumnByOverlap <-
    function(query, subject, column="ENTREZID", ...)
{
    olaps <- findOverlaps(query, subject, ...)
    f1 <- factor(subjectHits(olaps),
                 levels=seq_len(subjectLength(olaps)))
    splitAsList(mcols(query)[[column]][queryHits(olaps)], f1)
}