Weighted average in Azure Log Analytics

[elza_ts]

Hi everybody,
I'm new in Azure Log Analytics /KQL/
Language that AppInsights uses

How can i calculate weighted average?

Thank you

[#2]

// = (20 + 40 + 40 + 90 + 90 + 90) / 1 + 2 + 3

let t = datatable (Value:int, Weight:int)

[

20,1,

40,2,

90,3

];

t

| extend sumvalue = (Value * Weight)

| summarize weighted_avg = (sum(sumvalue) / sum(Weight) )

// = 61

[#3]

Hi Clive,
Thank you so much for your response. It is very helpful!

I also have column with weeks in my table, how can i calculate weighted_avg within each week?
In excel i usually do it using IF clause logic:
SUMPRODUCT(--(weeks!$C:$C=$A6),weight!$I:$I,value!$G:$G)/SUMIF(weeks!$C:$C,$A6,weight!$I:$I)

Can do it somehow like this in AppInsights?

[#4]

Hello,

Its always easier if you can provide the actual data or an example, what format is the "weeks" column in, is it a timestamp, a week number etc.... 

Would my datatable look like this?  

let t = datatable (Value:int, Weight:int, Week:string)

[

20,1,"Week1",

40,2,"Week2",

90,3,"Week3",

];

I assume you want to see a line that says:

Project <weighted avg>, <week name or number>

[#5]

i can provide screenshot, if it helps

i'm trying to analyzing response time here 

[#6]

How about this? 
The screenshot really helped, however you could have pasted the query and a line of data into this message as text, to save anybody having to re-type it, copy & paste is easier :)  This just helps us to help you faster, especially on a complex query or dataset.   I often add a line at the end of a test query "| limit 1", I can then copy the results of one line and column headings 

// = (20 + 40 + 40 + 90 + 90 + 90) / 1 + 2 + 3

let t = datatable (Value:int, Weight:int, Week:string)

[

10,1,"2019-02-25T00:00:00.000",

10,1,"2019-02-26T00:00:00.000",

20,1,"2019-02-25T00:00:00.000",

40,2,"2019-02-25T00:00:00.000",

90,3,"2019-02-26T00:00:00.000",

];

t

| extend sumvalue = (Value * Weight)

| summarize weighted_avg = (sum(sumvalue) / sum(Weight) ) by Week

[#7 · Accepted solution]

this is super weird. i had done the same thing with 'by Week' stuff before I replied to you.
and It didn't work. there was some mistake with 'By'.

and now it works! ha-ha
Thank you, Clive! You helped me a lot!

[#8]

Excellent, I'm pleased this is working for you now.  All the best, Clive