A formatted P value, roughly according to APA style
guidelines. This means that the noZero function is used to
remove the zero preceding the decimal point, and p values
that would round to zero given the requested number of digits
are shown as e.g. p<.001.
Arguments
values
The p-values to format.
digits
The number of digits to round to. Numbers smaller
than this number will be shown as <.001 or <.0001 etc.
spaces
Whether to include spaces between symbols,
operators, and digits.
includeP
Whether to include the 'p' and '='-symbol in the
results (the '<' symbol is always included).