How can I get the equation datas of a trendline in a chart

Aspose.Words Product Family
1

Hi,
I want to get the equation datas of a trendline in a chart and I can manage/edit only the template.
This is my code :

image.png1394×775 49.4 KB

and this is the result.

So, I want to get at the template level the “11740” value. How can I do that ?
Thank you in advance.

2

@deid

MS Word calculates an appoximation and draws a chart trendline on the fly. Unfortunately, there is no way to access data of the line.

3

@ivan.lyagin
Hi, thanks for your reply.
What a pity… and it"s not possible to calculate the line data, manually, from the data source of the chart ?
Thank you

4

@deid Sure, you can calculate slope value using your data. The formula for calculation is the following:

m=(N*∑xy - ∑x*∑y) / (N*∑x^2 - ∑x*∑x)

Where:

  • N is the number of data points
  • ∑xy is the sum of the product of each x and y value
  • ∑x is the sum of all x values
  • ∑y is the sum of all y values
  • ∑x^2 is the sum of the squares of all x values

In C# implementation this looks like this:

private static double CalculateLinearTrendlineSlope(PointF[] points)
{
    double n = points.Length;
    double xySum = points.Sum(p => p.X * p.Y);
    double xSum = points.Sum(p => p.X);
    double ySum = points.Sum(p => p.Y);
    double x2Sum = points.Sum(p => p.X * p.X);

    double slope = (n * xySum - xSum * ySum) / (n * x2Sum - xSum * xSum);

    return slope;
}

PointF[] points = new PointF[] { new PointF(1, 1), new PointF(2, 3), new PointF(3, 7) };
Console.WriteLine(CalculateLinearTrendlineSlope(points)); // Returns 3 for the given data

Offset can be calculated using the following formula:
B = (∑y - m*∑x)/N

Where m is a slope value calculated above:

private static double CalculateLinearTrendlineOffset(PointF[] points, double slope)
{
    double n = points.Length;
    double xSum = points.Sum(p => p.X);
    double ySum = points.Sum(p => p.Y);

    double offset = (ySum - slope * xSum) / n;

    return offset;
}
5

@alexey.noskov
Thank you, but I can do that in the template ? I can access to the POINT class ?

6

@deid The provided methods just demonstrates how the equation for linear trendline is calculated. You can put these methods into a custom class and register it as a known type. Then you can pass the data to these methods from your template and get the required values.

7

@alexey.noskov
yes I Know that this is a possibility and the best practice, but I can access only to the template (I can’t develop at the c# level) and no other implementations are planned at the C# level.
So I have to get out of it with what exists and do as much as possible in the template.
unfortunately I have this constraint :weary: :sob:

8

@deid @benestom You can implement the same in the template:

<<var [n=points.Length]>>
<<var [xySum = points.Sum(p => p.X * p.Y)]>>
<<var [xSum = points.Sum(p => p.X)]>>
<<var [ySum = points.Sum(p => p.Y)]>>
<<var [x2Sum = points.Sum(p => p.X * p.X)]>>
<<var [slope = (n * xySum - xSum * ySum) / (n * x2Sum - xSum * xSum)]>>
<<var [offset = (ySum - slope * xSum) / n]>>

Y=<<[slope]>>X<<if [offset>0]>>+<<[offset]>><<else>><<[offset]>><</if>>

PointF[] points = new PointF[] { new PointF(1, 1), new PointF(2, 3), new PointF(3, 7) };
            
Document doc = new Document(@"C:\Temp\in.docx");
ReportingEngine engine = new ReportingEngine();
engine.BuildReport(doc, points, "points");
doc.Save(@"C:\Temp\out.docx");

in.docx (14.2 KB)
out.docx (11.2 KB)

9

@alexey.noskov
Great !!! I try this… thank yo so much Alexey

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