Chart: Y-axis automatic logarithmic scale

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Laurent BP Laurent BP
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Chart: Y-axis automatic logarithmic scale

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Hello,

In ScaleAutomatism::calculateExplicitIncrementAndScaleForLogarithmic function [1], Y-axis automatic logarithmic scale is expand to B^0 (i.e. 1) in almost all cases.
In step 2, it is said [2]
/*  If minimum is less than 5 (i.e. original source values less than
    B^5, B being the base of the scaling), or if minimum and maximum
    are in different increment intervals (means, if minimum and maximum
    are not both in the range [B^n,B^(n+1)] for a whole number n), set
    minimum to 0, which results in B^0=1 on the axis. */
I do not agree with this comment because on a log scale, "1" has no special meaning: it is not the origin, like "0" is on a linear scale. I would propose a patch to suppress this part, but there are may be some good reasons to expand to 1?

I opened bug 96871 [3] about this.

Thanks in advance for your help.

Best regards,

Laurent BP

[1] http://opengrok.libreoffice.org/xref/core/chart2/source/view/axes/ScaleAutomatism.cxx#calculateExplicitIncrementAndScaleForLogarithmic
[2] http://opengrok.libreoffice.org/xref/core/chart2/source/view/axes/ScaleAutomatism.cxx#362
[3] https://bugs.documentfoundation.org/show_bug.cgi?id=96871
LibreOffice 5.3.5
Chris Sherlock Chris Sherlock
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Re: Chart: Y-axis automatic logarithmic scale

We have a class called “ScaleAutomism”?!?

Nice catch though.

Chris

> On 3 Jan 2016, at 11:46 PM, Laurent BP <[hidden email]> wrote:
>
> Hello,
>
> In ScaleAutomatism::calculateExplicitIncrementAndScaleForLogarithmic
> function [1], Y-axis automatic logarithmic scale is expand to B^0 (i.e. 1)
> in almost all cases.
> In step 2, it is said [2]
> /*  If minimum is less than 5 (i.e. original source values less than
>    B^5, B being the base of the scaling), or if minimum and maximum
>    are in different increment intervals (means, if minimum and maximum
>    are not both in the range [B^n,B^(n+1)] for a whole number n), set
>    minimum to 0, which results in B^0=1 on the axis. */
>
> I do not agree with this comment because on a log scale, "1" has no special
> meaning: it is not the origin, like "0" is on a linear scale. I would
> propose a patch to suppress this part, but there are may be some good
> reasons to expand to 1?
>
> I opened bug 96871 [3] about this.
>
> Thanks in advance for your help.
>
> Best regards,
>
> Laurent BP
>
> [1]
> http://opengrok.libreoffice.org/xref/core/chart2/source/view/axes/ScaleAutomatism.cxx#calculateExplicitIncrementAndScaleForLogarithmic
> [2]
> http://opengrok.libreoffice.org/xref/core/chart2/source/view/axes/ScaleAutomatism.cxx#362
> [3] https://bugs.documentfoundation.org/show_bug.cgi?id=96871
>
>
>
>
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> LibreOffice 5.0.2.2
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> View this message in context: http://nabble.documentfoundation.org/Chart-Y-axis-automatic-logarithmic-scale-tp4170678.html
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