nii.qc.volfrac: Fractional Volume
In TKoscik/nifti.qc: Quality control metrics and reports for NIFTI data

Calculate fractional volume.

1	nii.qc.volfrac(whole.nii, whole.vol=1L, whole.dir="eq", whole.thresh=1, part.nii, part.vol=1L, part.dir="eq", part.thresh=1)

`whole.nii`	Full directory listing to desired nifti image to use for masking the whole ROI (e.g., brain mask) (unzipped). Must be identical pixel dimensions to base image.
`whole.vol=1L`	For multi volume images; an integer indicating the volume to load (1..N)
`whole.dir="gt"`	Direction to threshold the mask image to generate the desired ROI. Options include ("gt") [>] Default, "ge" [>=], "lt" [<], "le" [<=], "eq" [==]
`whole.thresh=0`	Value at which to threshold the mask image to generate an ROI. E.g., for binary masks, where the value 1 indicates the ROI, default of >0, will generate the appropriate mask
`part.nii`	Full directory listing to desired nifti image to use for masking the part ROI (e.g., tissue mask) (unzipped). Must be identical pixel dimensions to base image.
`part.vol=1L`	For multi volume images; an integer indicating the volume to load (1..N)
`part.dir="gt"`	Direction to threshold the mask image to generate the desired ROI. Options include ("gt") [>] Default, "ge" [>=], "lt" [<], "le" [<=], "eq" [==]
`part.thresh=0`	Value at which to threshold the mask image to generate an ROI. E.g., for binary masks, where the value 1 indicates the ROI, default of >0, will generate the appropriate mask