Linear regression Linest_M + Linest_B

[#1]

Hi all,

I want to forecast the amount of orders for the coming months. I've created a master calendar which adds dates for + 1 year after the max date in the data (so that I can forecast multiple months ahead).

However, the linest_m and linest_b aren't calculating the correct numbers.

To calculate the forecast I'm using the following functions:

(LINEST_M( TOTAL Aggr(Count([Werkorder partner]), [Maand melding]), [Maand melding]) * NUM([Maand melding]) )+

LINEST_B(TOTAL Aggr(Count([Werkorder partner]), [Maand melding]), [Maand melding])

As you can see the X is 72,30, when I calculate it manually however I get: 903 / 8 = 112,875 and B -111,875.

I've tried forcing the graph to start in (0,0) with

(LINEST_M( TOTAL Aggr(Count([Werkorder partner]), [Maand melding]), [Maand melding],0,0)

but this returns x as 6945,5948???

The correct formula (I think) should be: 112,875X - 111,875. Just have to get qlik to understand that

[Gysbert_Wassenaar]

The chart doesn't start at 0. It starts at Jan. That's the first 'row' of the chart.

[swuehl · Accepted solution]

Please have a look at

Matching linest_m and linest_b function to auto-generated trendline

[#4]

So you suggest I should use linest_m( ....,..., 0,1)? I'll test it tonight.

[#5]

I'm not sure if I understand the post, you suggest to rank the month dimension in the linest_ functions?

[#6]

Converting the dimension doesn't fixed the problem.

[swuehl]

Could you upload a small sample QVW?

[#8]

Okay got the linear regression correct, as in equal to the one qlikview calculates. But I still think the regression should be 112,875X - 111,875 not 72,30x + 150,44 as qlikview calculates. I think this has to do with the fact that a count of the orders in january returns null, as well as okt nov dec.