showing float/double axis labels

[Malcolm Wallace]

I just came across a small anomaly, where a Chart axis was labelled
with the following sequence of values:

-0.15
-0.1
-5.0e-2
0
5.0e-2
0.1
0.15
0.2

Does anyone else think that the labels for +/-0.05 look out-of-place?
The reason we get 5.0e-2 instead of 0.05 is because we use plain
"show" on labels, and this is the standard haskell behaviour for
showing Float/Double.

The attached patch changes the label-showing function from "show" to
"Numeric.showFFloat", which never uses scientific notation. Whilst it
makes the anomalous example look better, I am not convinced it is
necessarily the best solution for all situations. Any thoughts?

Regards,
Malcolm

[Malcolm Wallace]

> The attached patch changes the label-showing function from "show" to
> "Numeric.showFFloat", which never uses scientific notation.

Actually, that was an incorrect version of the patch. I attach a
corrected version.

Regards,
Malcolm

[Tim Docker]

I've pushed this, thanks.

I agree that a more complex algorithm may be better in the general case,
but this is still
better than the plain old Show that we have now.

Tim

[Malcolm Wallace]

I attach an additional patch, which allows the user to supply their
own axis-labelling function to override the default. I use this with
e.g.

dollar, percent :: Double -> String
dollar v = "$"++ show v
percent v = show (v*100) ++ "%"

I am not completely satisfied with this, because although labelling
for most types can be overridden, labelling for dates/times is not,
even if you pass in a custom labeller. But this does an adequate job
for the simpler types.

Regards,
Malcolm

[Tim Docker]

> I attach an additional patch, which allows the user to supply their
> own axis-labelling function to override the default. I use this with
> e.g.
>
> dollar, percent :: Double -> String
> dollar v = "$"++ show v
> percent v = show (v*100) ++ "%"
>
> I am not completely satisfied with this, because although labelling
> for most types can be overridden, labelling for dates/times is not,
> even if you pass in a custom labeller. But this does an adequate job
> for the simpler types.
>
> Regards,
> Malcolm

Can you given an example of how this would be used? Is it meant to
simplify the existing way of doing this, which would be something like:

layout = layout1_title ^= "Price History"
...
$ layout1_left_axis ^: laxis_generate ^= autoScaledAxis lap
$ defaultLayout1

lap =defaultLinearAxis{la_labelf_=dollar}

Tim