1 /* Inspired by Lee Byron's test data generator. */

     2 function stream_layers(n, m, o) {

     3   if (arguments.length < 3) o = 0;

     4   function bump(a) {

     5     var x = 1 / (.1 + Math.random()),

     6         y = 2 * Math.random() - .5,

     7         z = 10 / (.1 + Math.random());

     8     for (var i = 0; i < m; i++) {

     9       var w = (i / m - y) * z;

    10       a[i] += x * Math.exp(-w * w);

    11     }

    12   }

    13   return d3.range(n).map(function() {

    14       var a = [], i;

    15       for (i = 0; i < m; i++) a[i] = o + o * Math.random();

    16       for (i = 0; i < 5; i++) bump(a);

    17       return a.map(stream_index);

    18     });

    19 }

    20 

    21 /* Another layer generator using gamma distributions. */

    22 function stream_waves(n, m) {

    23   return d3.range(n).map(function(i) {

    24     return d3.range(m).map(function(j) {

    25         var x = 20 * j / m - i / 3;

    26         return 2 * x * Math.exp(-.5 * x);

    27       }).map(stream_index);

    28     });

    29 }

    30 

    31 function stream_index(d, i) {

    32   return {x: i, y: Math.max(0, d)};

    33 }