Erlang C - Error in FACT () and POWER() DAX FUNCTIONS

[Anonymous]

Hi!

Has anyone tried to figure out how to calculate Erlang C formula with DAX? I am trying to calculate the number of agents needed for a specific level of service for a call centre.

I have followed this tutorial "Creating a Call Center staffing tool in Power PIvot" by Josh Miller. It was very helpful but Power BI is showing computing limitations, specifically is given me these errors:

“MdxScript(Model) (6,5) Calculation error in measure 'Table'[TA_INTERACTIONS]’: An argument of function FACT has the wrong data type or the result is too large or too small."

“MdxScript(Model) (25, 75) Calculation error in measure 'Table'[TA_INTERACTIONS]’: An argument of function POWER has the wrong data type or the result is too large or too small."

Calculations are based on Poisson and Cumulative Poisson formula, which contains a POWER() and FACT() functions:

a) Poisson:

PoissonX =
DIVIDE (
    EXP ( - [IntensidadTraf] )
        * POWER ( [IntensidadTraf]; SUM ( AgentsX[AgentsX] ) );
    FACT ( SUM ( AgentsX[AgentsX] ) );
    0
)

b) Cumulative Poisson

PoissonC_X =
SUMX (
    FILTER ( AgentsZ; AgentsZ[AgentsZ] < SUM ( AgentsX[AgentsX] ) );
    DIVIDE (
        EXP ( - [IntensidadTraf] ) * POWER ( [IntensidadTraf]; AgentsZ[AgentsZ] );
        FACT ( AgentsZ[AgentsZ] );
        0
    )
)

Where ‘AgentsX [AgentsX] ’ and ‘AgentsZ [AgentsZ] ’ are tables containing only one column with the total number of agents, increasing the value 1 by 1.

The model works for less than 150 agents but breaks at 151 agents or greater.

Any ideas on how to solve it?

Thanks!

[AZJohnPowerBI]

I also found this helps too!
https://forum.enterprisedna.co/t/analysing-call-center-data/3146/2

[AZJohnPowerBI]

How long of intervals were you using to figure (A) or Call intensity? Generally, something around 15 minutes - 30 minutes should work. There are some problems with the Erlang formula, in that the accuracy was only meant for ~143 agents. Anything above that, and it begins to break down.
I found this site fairly helpful on problemsolving and and overall helpful resource.

Sorry I wasn't able to find a solution to what to do if you have more agents than the Erlang calculations can handle, and I wish you well.

[srikanthG]

Hello Judy,

Have you resolved the Erlang - C logic issues or found any alternative solution?

[Jorgast]

Unfortunately Not yet

[v-shex-msft]

Hi @Anonymous ,

Actually, it mean you are use too large number to do 'fact' calculation and the result number is over int type limit.(I test on my side and I it can calculate with numbers less than 171)

Regards,
Xiaoxin Sheng

[Anonymous]

Thanks @v-shex-msft !

Though i need a much higher number to figure out my calculations. I will keep on searching an alternative.

Regards.

[Jorgast]

@Anonymous 

I am trying to calculate call volume using Erlang C and Power BI variables. I am getting an error similiar to what you had. Were you able to find a way to forecast call volume in Power BI using Erlang?