Using valueRange with Logscale and yRangePad has unexpected results

[action0jackson]

Please refer to this article: http://stackoverflow.com/questions/32609202/dygraphs-using-valuerange-with-logscale

[klausw]

I think there's at least two issues here:

https://github.com/danvk/dygraphs/blob/master/src/dygraph.js#L2638

      if (!ypadCompat) {
        if (axis.logscale) {
          var logpad = Math.exp(Math.log(span) * ypad);
          y0 *= logpad;
          y1 /= logpad;
        } else {
          span = y1 - y0;
          y0 -= span * ypad;
          y1 += span * ypad;
        }
      }

First problem is that "axis.logscale" is always false, the axis object doesn't have this property. So the conditional is always false in yRangePad + logscale + valueRange mode, and it inappropriately takes the branch below for a linear scale.

Next problem is that it adjusts in the wrong direction - should be:

          y0 /= logpad;
          y1 *= logpad;

If I make these changes in an interactive session, it looks much more reasonable, though the padding amount isn't quite right - I seem to get just ~3 pixels of padding after requesting 10 pixels.

[klausw]

Here's an updated jsfiddle - the original one didn't work for me: http://jsfiddle.net/hg0nfytr/5/

The default yrange = 0.25005,3 shows the issue, the y axis starts at 1.00e-4. Setting ymin to <= 0.25 breaks the graph entirely.

[action0jackson]

Just an fyi I updated the original fiddle to work: http://jsfiddle.net/85f1ga5e/

[klausw]

Proposed fix + regression tests in #732 . The padding is now pixel-accurate in logscale.

[klausw]

Fix is merged in master. Looks like I can't close the bug though.