code: function(meanlog, sdlog) {
           return {
              d: function(x, logp) { return dlnorm(meanlog, sdlog, logp)(x); },
              p: function(q, lowerTail, logp) {
                 return plnorm(meanlog, sdlog, lowerTail, logp)(q);
              },
              q: function(p, lowerTail, logp) {
                 return qlnorm(meanlog, sdlog, lowerTail, logp)(p);
              },
              r: function() { return rlnorm(meanlog, sdlog)(); }
           };
        }
docs: Returns an object representing a normal distribution, with properties `d`, `p`, `q`, `r`.
  ```
  lognormal(meanlog, sdlog).d(x, logp)            // same as dlnorm(meanlog, sdlog, logp)(x)
  lognormal(meanlog, sdlog).p(x, lowerTail, logp) // same as plnorm(meanlog, sdlog, lowerTail, logp)(x)
  lognormal(meanlog, sdlog).q(x, lowerTail, logp) // same as qlnorm(meanlog, sdlog, lowerTail, logp)(x)
  lognormal(meanlog, sdlog).r()                   // same as rlnorm(meanlog, sdlog)()
  ```
  @memberof lognormal