Function randomBeta

external/.d3.js:14639–14646

(alpha, beta)

  var G = gamma.source(source);

  function randomBeta(alpha, beta) {
    var X = G(alpha),
        Y = G(beta);
    return function() {
      var x = X();
      return x === 0 ? 0 : x / (x + Y());
    };
  }

  randomBeta.source = sourceRandomBeta;