# office message

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*Subject*: **OFFICE-2119 date axis, here logarithmic scale**

*From*: **Regina Henschel <regina.henschel@libreoffice.org>**
*To*: ODF member <office@lists.oasis-open.org>
*Date*: Tue, 19 Sep 2017 14:16:15 +0200

Hi members,

`the attached documents contain charts to illustrate, why I think, we
``should not allow a logarithmic date axis.
`
Below the charts are screenshots of the axis settings in LibreOffice.

`The file is "ODF 1.2 extended" with the LibreOffice extensions,
``otherwise you would not get the date axis in the line chart.
`

`The sheet "Real" contains the line chart with date axis. I have chosen
``the unit day, because then you get the same distance of 1 as with the
``number interpretation of a date.
`

`The next chart is an XY-chart with the same axis settings as in the line
``chart. From the included regression curve you can see, that LibreOffice
``indeed uses the internal number of a date for calculating.
`

`The third chart is an XY-chart with logarithmic x-axis scaling. I have
``uses that, because a logarithmic scaling is not possible for a line
``chart in LibreOffice (and should not become possible). If you want to
``get some grid lines and labels, you need a very small "major interval".
``The chosen value 0.05 has no special meaning and are only used for to
``get some grid lines.
`

`You will notice, that the curve and the grid in linear and logarithmic
``scale are nearly the same, so using logarithmic scale gives no further
``insights.
`

`The sheet "Fake" contains two XY-charts, where I have shifted the null
``date by subtraction of 40179. The UI of LibreOffice has no option to set
``the null date to an arbitrary value. I have extended the x-values to
``cover the values in column A too and then used these high values for a
``secondary x-axis. The label of this secondary x-axis is shown as date
``values. The labels of the first x-axis are not shown, but the first
``x-axis is used for calculating the regression curve. Therefore you get
``here a different equation than on the sheet "Real".
`

`Here too the "major interval" value in the logarithmic scale is a small
``decimal, otherwise you get not enough labels. So this shows, that
``shifting the null date would not solve the problem, that integer values
``for the "major interval" do not allow useful grids and labels.
`
Kind regards
Regina

**Attachment:
**`DateAxis.ods`

*Description:* application/vnd.oasis.opendocument.spreadsheet

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