docs: function pt(df, lowerTail, logp) {
        var ptl;
  
        lowerTail = lowerTail !== false;
        logp = logp === true;
        ptl = ptlog(df, lowerTail);
        if (df === Infinity) { return normal.pnorm(0, 1, lowerTail, logp); }
        return logp ? ptl : function(x) { return Math.exp(ptl(x)); };
     }