In Section 20.43 chart:regression-type add the following item to the list (sub- and superscript seems to not work properly, but I think, you know to write a polynomial in x of degree n):
- polynomial - Polynomial regression - approximate the values of the series using the model: y = A~0~ + A~1~ x + A~2~ x^2^ + ... + A~n~ x^n^ where n is given by the chart:regression-max-degree attribute.
The generated attribute list changes to:
The values of the chart:regression-type attribute are none, linear, logarithmic, exponential, power and polynomial.
Add these new sections in chapter 20
chart:regression-max-degree
The chart:regression-max-degree attribute specifies the maximum degree of a polynomial regression curve. This attribute is only evaluated together with attribute chart:regression-type and if that has the value polynomial.
The value of the chart:regression-max-degree attribute must be greater than or equal to 2.
The default value for this attribute is 2.
The generated text is then:
The chart:regression-max-degree attribute is usable with the following element: <style:chart-properties> 17.22.
The chart:regression-max-degree attribute has the data type positiveInteger.
chart:regression-force-intercept
The chart:regression-force-intercept attribute specifies whether a regression curve of type linear, exponential or polynomial must intercept the y-axis at a certain value.
The defined values for the chart:regression-force-intercept attribute are:
• true: The regression curve intercepts the y‑axis at the value, which is defined by the chart:regression-intercept-value attribute.
• false: The interception of regression-curve and y-axis is calculated from the data series.
The default value for this attribute is false.
This attribute is only evaluated together with attribute chart:regression-type and if that has one of the following values: linear, exponential or polynomial.
The generated text is then:
The chart:regression-force-intercept attribute is usable with the following element: <style:chart-properties> 17.22.
The chart:regression-force-intercept attribute has the data type boolean.
chart:regression-intercept-value
The chart:regression-intercept-value attribute specifies where a regression curve must intercept the y-axis, if attribute chart:regression-force-intercept is true.
This attribute is only evaluated together with chart:regression-force-intercept attribute.
The default value for this attribute is 0 in case of regression type linear or polynomial, and the default value is 1 in case of regression type exponential.
The generated text is then:
The chart:regression-intercept-value attribute is usable with the following element: <style:chart-properties> 17.22.
The chart:regression-intercept-value attribute has the data type double.
chart:regression-name
The chart:regression-name attribute specifies a name of a regression curve.
Default value is an empty string.
The generated text is then:
The chart:regression-name attribute is usable with the following element: <style:chart-properties> 17.22.
The chart:regression-name attribute has the data type string.
The needed change to the schema is given by this diff:
--- OpenDocument-schema-v1.3_ohneTab.rng 2018-06-06 00:01:34.171094900 +0200
+++ OpenDocument-schema-v1.3_regression_curve1.rng 2018-06-05 23:59:49.276136600 +0200
@@ -9993,14 +9993,35 @@
<rng:value>none</rng:value>
<rng:value>linear</rng:value>
<rng:value>logarithmic</rng:value>
<rng:value>exponential</rng:value>
<rng:value>power</rng:value>
+ <rng:value>polynomial</rng:value>
</rng:choice>
</rng:attribute>
</rng:optional>
<rng:optional>
+ <rng:attribute name="chart:regression-max-degree">
+ <rng:ref name="positiveInteger"/>
+ </rng:attribute>
+ </rng:optional>
+ <rng:optional>
+ <rng:attribute name="chart:regression-force-intercept">
+ <rng:ref name="boolean"/>
+ </rng:attribute>
+ </rng:optional>
+ <rng:optional>
+ <rng:attribute name="chart:regression-intercept-value">
+ <rng:ref name="double"/>
+ </rng:attribute>
+ </rng:optional>
+ <rng:optional>
+ <rng:attribute name="chart:regression-name">
+ <rng:ref name="string"/>
+ </rng:attribute>
+ </rng:optional>
+ <rng:optional>
<rng:attribute name="chart:axis-position">
<rng:choice>
<rng:value>start</rng:value>
<rng:value>end</rng:value>
<rng:ref name="double"/>