Use 2 variable in a math expression

Elastic Stack Kibana
#1

I am running 7.9.1 and am trying to perform math with 2 variables like below. Is this possible?

filters
| timefilter field="@timestamp" from="now-1d" to="now"
| var_set name="completed" value={escount index="index_1" query="thisField:test AND status:completed"}
| var_set name="sent" value={escount index="index_1" query="thisField:test AND status:sent"}
| math "completed / sent"
#2

Hi, welcome back! It looks like you are trying to do what we would call a "filter ratio".

Honestly, I think string concatenation is the easiest way to do this.

var_set name="errors" value=10
| var_set name="total" value=100
| math {string value={var "errors"} value=" / " value={var "total"}}

This is because the math function typically works using data tables, but we don't have a nice function to create tables in Canvas.

#3

Thanks for the welcome back and the response. I am able to get part of the way there now.

var_set name="completed" value={escount index="index_1" query="thisField:test AND status:completed"}
| var_set name="sent" value={escount index="index_1" query="thisField:test AND status:sent"}
| math {string value={var "completed"} value=" / " value={var "sent"}}

However, if I want to restrict the result from the queries to the last 24 hours it won't work. How can I apply the timefilter that i specified in my original post?

#4

One thing that is not obvious is the way that parameters are passed into datasources in sub-expressions. For example, the filters is implicitly sent into escount here:

filters
| var_set name="completed" {/* implicit filters | */ escount}

But then when you have two var_set calls in a row, the same behavior causes an error:

var_set name="completed" value=0
| var_set name="sent" value={escount}

Putting this together, you need to create the full chain of datafetching at each subexpression level.

In this case I also used a time filter control, but you can do it either way:

timefilterControl compact=true column="@timestamp" filterGroup="myGroup"
| render


var_set name="completed" value={filters | timefilter filterGroup="myGroup" | escount index="kibana_sample_data_logs" query="bytes:[100 TO *]"}
| var_set name="sent" value={filters | timefilter filterGroup="myGroup" | escount index="kibana_sample_data_logs" query="*"}
| math {string {var "completed"} " / " {var "sent"}}
#5

Wylie, thank you for the help and I now have things working. I'll figure out the expression language at some point. :slight_smile: