Find polynomial equation

[patsa7]

Hi all,

The latest update of PowerBi supports the linest function.

However, I am trying to use it in the same way, as in MS Excel, but it is now working.

In particular, I want to find the polynomial function that connects two columns of a table.

Further to the above i tried using the follow functions (in measures) to find a, b... etc of the polynomial equation

y = a*x4 + b*x3 + c*x2 + d*x + e 

a=INDEX(LINEST(known_y,known_x^{1,2,3,4}),1)

b=INDEX(LINEST(known_y,known_x^{1,2,3,4}),1,2)

....

Since the above measures are not working, I would appreciate if you could advise how to resolve it.

Thank you.

[patsa7]

Thank you for your replies. I understand that there is no way to find a polynomial equation of 4th grade through MS PowerBi , in as similar manner as in MS Excel.

[ronrsnfld]

Just saw this question as I was looking for a method to do this in M.

But do do this in DAX is relatively easy as LINESTX accepts multiple arguments for "X"

Starting with a table:

Add columns representing successive powers of X:

 Example for X^2:    X^2 = POWER([X],2)

Then use this to create a new table with the relevant slopes (and other coefficients)

TableName = = LINESTX(Example4th,[Y],[X],[X^2],[X^3],[X^4])

This results in:

as well as other coefficients.

Hope this helps, although late.

[technologyLMM]

Thank you for your reply @Padycosmos . The mentioned guide describes how to find the polynomial of 1st grade and not of 4th grade, as i would like. 

y = a*x^4 + b*x^3 + c*x^2 + d*x + e 

Could you please give me an example on how to use this function to find a, b,c ,d and e of the above polynomial equation?

[Padycosmos]

Sorry, I have never tried this before. Shall get back after trying it out

[Padycosmos]

Hope this helps:

https://dax.guide/linest/#:~:text=LINEST%20DAX%20Function%20(Math%20and%20Trig)&text=Uses%20the%20Le....