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util.js
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util.js
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(function() {
this.swiss_roll = function(N) {
var r = numeric.linspace(0, 1, N);
var t = numeric.mul(3 * Math.PI / 2, numeric.add(1, numeric.mul(2, r)));
var x = numeric.mul(3, numeric.mul(t, numeric.cos(t)));
var y = numeric.mul(3, numeric.mul(t, numeric.sin(t)));
var z = numeric.add(-30, numeric.mul(60, numeric.random(N)));
return numeric.transpose([x, y, z]);
};
function insort(items, x, k) {
for (var i = 0; i < k; i++) {
if (x < items[i]) {
items.splice(i, 0, x);
items.pop();
return items[k-1];
}
}
return items;
}
function pdist(data) {
var i, j, n = data.nr;
var dists = numeric.zeros(n, n);
var a, di, dj;
for (i = 0; i < n; i++) {
a = data.row(i);
di = dists.row(i);
for (j = 0; j < i; j++) {
dj = dists.row(j);
di[j] = dj[i] = numeric.l2dist(a, data.row(j));
}
di[i] = 0;
}
return dists;
}
this.knn = function(data, k) {
var dists = pdist(data);
var n = dists.nr;
var results = new Array(n);
var minvals = new Array(k);
var d, maxmin, min_k_idx, di;
var j = 0;
for (var i = 0; i < n; i++) {
di = dists.row(i);
minvals.fill(Infinity);
maxmin = Infinity;
for (j = 0; j < n; j++) {
d = di[j];
if (d > 0 && d < maxmin) {
maxmin = insort(minvals, d, k);
}
}
min_k_idx = [];
for (j = 0; j < n; j++) {
d = di[j];
if (d > 0 && d <= maxmin) {
min_k_idx.push(j);
}
}
results[i] = min_k_idx;
}
return [results, dists];
};
this.scale_dimensions = function(X, scale) {
var num_dims = X.nc,
num_pts = X.nr;
var col_mins = new Float32Array(num_dims),
col_maxs = new Float32Array(num_dims);
col_maxs.set(X.row(0));
col_mins.set(col_maxs);
var data = X.data;
var i, j, x, idx = num_dims;
for (i = 1; i < num_pts; i++) {
for (j = 0; j < num_dims; j++) {
x = data[idx++];
if (x < col_mins[j]) {
col_mins[j] = x;
} else if (x > col_maxs[j]) {
col_maxs[j] = x
}
}
}
// convert to 0,2 range
var ranges = numeric.sub(col_maxs, col_mins);
numeric.diveq(ranges, 2);
idx = 0;
for (i = 0; i < num_pts; i++) {
for (j = 0; j < num_dims; j++) {
data[idx] -= col_mins[j];
data[idx++] /= ranges[j];
}
}
// convert to -scale,+scale range
numeric.subeq(data, 1);
numeric.muleq(data, scale);
}
this.adj_matrix = function(nn_inds, dists) {
var i, j, k, n = dists.nr;
var nns, di, adj_i, adj_j;
var adj = numeric.zeros(n, n);
adj.data.fill(Infinity);
for (i = 0; i < n; i++) {
nns = nn_inds[i];
di = dists.row(i);
adj_i = adj.row(i);
for (j = 0; j < nns.length; j++) {
k = nns[j];
adj_i[k] = di[k];
}
adj_i[i] = 0;
}
// symmetrize
for (i = 0; i < n; i++) {
adj_i = adj.row(i);
for (j = 0; j < n; j++) {
adj_j = adj.row(j);
if (adj_i[j] === Infinity) {
if (adj_j[i] !== Infinity) {
adj_i[j] = adj_j[i];
}
} else if (adj_j[i] === Infinity) {
adj_j[i] = adj_i[j];
}
}
}
return adj;
}
}).call(this);