cv
cross-validation settings, can be a number or a list. If cv is a number, it will be
used as a number of segments for random cross-validation (if cv = 1, full cross-validation
will be preformed), if it is a list, the following syntax can be used: cv = list('rand', nseg, nrep)
for random repeated cross-validation with nseg segments and nrep repetitions or cv = list('ven', nseg)
for systematic splits to nseg segments ('venetian blinds').