I am working on using the SomaticSignatures package on a list of mutations I've received from a collaborator.  The file has all the variants listed in a tab-delimited text file, with all the fields you would expect from an annotated vcf file (e.g. Chromosome, Start_Position, End_Position, Reference_Allele, Tumor_Seq_allele, etc) named "CCCC_muts"

In order to get this working, I'm trying to create a VRanges object from this text file.  I ran the following command to try to accomplish this:

mutations <- VRanges(
     seqnames = seqnames(as.character(CCCC_muts$Chromosome)),
     ranges = ranges(CCCC_muts, start = CCCC_muts$Start_Position, end = CCCC_muts$End_Position),
     ref = CCCC_muts$Reference_Allele,
     alt = CCCC_muts$Tumor_Seq_Allele2,
     sampleNames = CCCC_muts$Barcode
)

I'm getting an error:

Error in (function (classes, fdef, mtable)  : 
  unable to find an inherited method for function ‘ranges’ for signature ‘"X"’

(where X is whatever type of data I try to put into it)

Because I'm unsure how to create the proper ranges format from my CCCC_muts file, and perhaps because of some other reason I don't understand.  Any help in resolving this issue would be awesome.

I think you want something like:

mutations <- with(CCCC_muts, VRanges(
    seqnames = Chromosome,
    ranges = IRanges(Start_Position, End_Position),
    ref = Reference_Allele,
    alt = Tumor_Seq_Allele2,
    sampleNames = Barcode
))