+ * Transforms layout_.points index into data row number.
+ * @param int layout_.points index
+ * @return int row number, or -1 if none could be found.
+ * @private
+ */
+Dygraph.prototype.idxToRow_ = function(idx) {
+ if (idx < 0) return -1;
+
+ for (var i in this.layout_.datasets) {
+ if (idx < this.layout_.datasets[i].length) {
+ return this.boundaryIds_[0][0]+idx;
+ }
+ idx -= this.layout_.datasets[i].length;
+ }
+ return -1;
+};
+
+/**