constructor function for virtual class BrainVector
BrainVector(data, space = NULL, mask = NULL, source = NULL, label = "")matrix, a 4d array, or a list of BrainVolumes. 
If the latter, the geometric space of the data BrainSpace will be inferred from the constituent volumes, 
which must all be identical.BrainSpace object. Does not ned to be included if data argument is a list of BrainVolumesarray of type logicalBrainSource objectcharacterBrainVector class. 
If mask is provided then SparseBrainVector, otherwise DenseBrainVector