+ var area = this.plotter_.area;
+ var yRange = this.yAxisRange(axis);
+
+ if (!axis.logscale) {
+ return yRange[0] + (area.h - y) / area.h * (yRange[1] - yRange[0]);
+ } else {
+ // Computing the inverse of toDomCoord.
+ var pct = (y - area.y) / area.h
+
+ // Computing the inverse of toPercentYCoord. The function was arrived at with
+ // the following steps:
+ //
+ // Original calcuation:
+ // pct = (logr1 - Dygraph.log10(y)) / (logr1 - Dygraph.log10(yRange[0]));
+ //
+ // Move denominator to both sides:
+ // pct * (logr1 - Dygraph.log10(yRange[0])) = logr1 - Dygraph.log10(y);
+ //
+ // subtract logr1, and take the negative value.
+ // logr1 - (pct * (logr1 - Dygraph.log10(yRange[0]))) = Dygraph.log10(y);
+ //
+ // Swap both sides of the equation, and we can compute the log of the
+ // return value. Which means we just need to use that as the exponent in
+ // e^exponent.
+ // Dygraph.log10(y) = logr1 - (pct * (logr1 - Dygraph.log10(yRange[0])));
+
+ var logr1 = Dygraph.log10(yRange[1]);
+ var exponent = logr1 - (pct * (logr1 - Dygraph.log10(yRange[0])));
+ var value = Math.pow(Dygraph.LOG_SCALE, exponent);
+ return value;
+ }
+};
+
+/**
+ * Converts a y for an axis to a percentage from the top to the
+ * bottom of the div.
+ *
+ * If the coordinate represents a value visible on the canvas, then
+ * the value will be between 0 and 1, where 0 is the top of the canvas.
+ * However, this method will return values outside the range, as
+ * values can fall outside the canvas.
+ *
+ * If y is null, this returns null.
+ * if axis is null, this uses the first axis.
+ */
+Dygraph.prototype.toPercentYCoord = function(y, axis) {
+ if (y == null) {
+ return null;