Convert various input as features to a vector for fucntions that
do not support multi-word features e.g.
dfm_select, sequences, collocations.
features2vector(features)the input features, one of:
character vector, whose elements will be split on whitespace;
list of characters, consisting of a list of token patterns, separated by white space;
tokens object;
dictionary object;
collocations object.
an unnamed vector of features