topic Extracting Polynomial equation formula from trendline in QlikView

Extracting Polynomial equation formula from trendline

Mon, 18 Feb 2013 17:31:17 GMT

Hi,

I am trying to build a table with a forecast column using the values from the polynomial trendlines and then extract the formula (i.e. y = a2x^2 + a1x + b).

I know how to do this for linear trendline (y=mx+b), using:

m = LINEST_M(Aggr(sum(Xval),Yval),Yval)

b = LINEST_B(Aggr(sum(Xval),Yval),Yval)

I can then use these values in straight table to make a forecast column in my table. However, this is less acurate than the polynomial equation. Are there equvilent functions to calculate the polynomial constants?

Thanks in advance,

Dave

Re: Extracting Polynomial equation formula from trendline

Gysbert_Wassenaar — Mon, 18 Feb 2013 17:56:50 GMT

No, that's not possible. But you can add a polynomial trendline of 2nd to 4th degree and check the option Show Equation. If you need more statistic functions you need something like the R integration kit.

Re: Extracting Polynomial equation formula from trendline

Mon, 18 Feb 2013 18:01:36 GMT

Ok, thanks!