- // special case: if we have no sense of scale, use +/-10% of the sole value.
- if (span === 0) { span = maxY; }
+ // special case: if we have no sense of scale, center on the sole value.
+ if (span === 0) {
+ if (maxY !== 0) {
+ span = Math.abs(maxY);
+ } else {
+ // ... and if the sole value is zero, use range 0-1.
+ maxY = 1;
+ span = 1;
+ }
+ }
+
+ // Add some padding. This supports two Y padding operation modes:
+ //
+ // - backwards compatible (yRangePad not set):
+ // 10% padding for automatic Y ranges, but not for user-supplied
+ // ranges, and move a close-to-zero edge to zero except if
+ // avoidMinZero is set, since drawing at the edge results in
+ // invisible lines. Unfortunately lines drawn at the edge of a
+ // user-supplied range will still be invisible. If logscale is
+ // set, add a variable amount of padding at the top but
+ // none at the bottom.
+ //
+ // - new-style (yRangePad set by the user):
+ // always add the specified Y padding.
+ //
+ var ypadCompat = true;
+ var ypad = 0.1; // add 10%
+ if (this.attr_('yRangePad') !== null) {
+ ypadCompat = false;
+ // Convert pixel padding to ratio
+ ypad = this.attr_('yRangePad') / this.plotter_.area.h;
+ }