Format option for log scale.

[jonathanBieler]

Sometimes I'd like my axis to be labelled 1, 10, 100 instead of 10^0, 10^1, 10^2. I thought the format option should do that (Scale.x_log10(format=:plain)) but apparently that's not the case. Actually setting the format to scientific labels things 10^1x10^0 which is not very useful.

I know that I can use the labels option to format my labels, but we could probably make better use of the format option here, no ?

[Mattriks]

As you note, the difference between format and labels is:

• format changes the notation of numbers in the label
• labels is used to change the label format e.g. 10² or 100 or e^4.60517

The notation of numbers is changed via the function showoff e.g. Gadfly.showoff([10.0], :scientific), which is then passed to the labelling function.

To change this, some design discussion would be needed, so please outline your ideas about notation and labelling.

[jonathanBieler]

I would just do something like this for log10_formatter :

function log10_formatter(xs::AbstractArray, format=:scientific) 
    if format == :plain
        return [@sprintf("%s", x) for x in showoff((x -> 10^x).(xs), format)]
    else
        return [@sprintf("10<sup>%s</sup>", x) for x in showoff(xs, :plain)]
    end
end

Which seems to work fine except I'm getting to many decimals displayed in the plain format.

Basically make the scientific format the default for log scales (10^x is the scientific format after all).

[bjarthur]

+10^2 for making it easy to display 100! :)

i like @jonathanBieler 's approach.

lots of decimals are displayed by showoff because it is being called with an extended range of tick marks, not just the ones displayed. put @info xs into the code in the preceeding comment to demonstrate. one can suppress this behavior by setting extend_tick to false here. i believe the reason for the extension is to facilitate panning and zooming in SVGJS. the code which decides what extra tick marks to add seems to presume a linear scale. not sure how best to change it for log scales.