# Arithmetic with string **URL:** https://discuss.elastic.co/t/arithmetic-with-string/52131 **Category:** Logstash **Created:** [June 7, 2016, 10:19pm UTC](https://discuss.elastic.co/t/arithmetic-with-string/52131 "2016-06-07T22:19:57Z") **Posts on this page:** 7 **Page:** 1
### Author: ![stecino](https://avatars.discourse-cdn.com/v4/letter/s/ea666f/32.png) [@stecino](https://discuss.elastic.co/u/stecino) #### Post date: [June 7, 2016, 10:19pm UTC](https://discuss.elastic.co/t/arithmetic-with-string/52131/1 "2016-06-07T22:19:57Z")
Hello, I have a string "5.34" and I am trying to multiply it by number, say 1000. Can I do it with gsub or ruby plugin. I have read that ruby plugin is resource intensive, so i would prefer to do it with gsub if possible. ---
### Author: ![magnusbaeck](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/magnusbaeck/32/44943_2.png) [@magnusbaeck](https://discuss.elastic.co/u/magnusbaeck) #### Post date: [June 10, 2016, 5:40am UTC](https://discuss.elastic.co/t/arithmetic-with-string/52131/2 "2016-06-10T05:40:04Z")
Don't assume that regular expression substitutions are slower than ruby filters. Measure! Do your strings always have two decimals? ---
### Author: ![stecino](https://avatars.discourse-cdn.com/v4/letter/s/ea666f/32.png) [@stecino](https://discuss.elastic.co/u/stecino) #### Post date: [June 10, 2016, 7:06pm UTC](https://discuss.elastic.co/t/arithmetic-with-string/52131/3 "2016-06-10T19:06:40Z")
I am not sure, but from the rounding, most likely it will have two decimal points. Here is what I have input { stdin { codec =\> json } } output { stdout { codec =\> rubydebug { metadata =\> true } } } filter { mutate { add\_field =\> { "Test1"=\> "%{Test}" } convert =\> { "Test1" =\> "float"} } ruby {code =\> "event['foo'] = event['Test1'] \* 1000"} } I ran echo '{"Test":"5.34"}' | ../../bin/logstash -f ../test.config Here is the snippet from resulting JSON ``` "Test1" => "5.34", "foo" => "5.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.345.34" ``` } Shouldn't it multiply instead? I can gsub . with "" but I need to count the number of places I need to move the decimal point. ---
### Author: ![Christian\_Dahlqvist](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/christian_dahlqvist/32/4617_2.png) [@Christian\_Dahlqvist](https://discuss.elastic.co/u/Christian_Dahlqvist) #### Post date: [June 10, 2016, 7:09pm UTC](https://discuss.elastic.co/t/arithmetic-with-string/52131/4 "2016-06-10T19:09:53Z")
The JSON you passed in has the value represented as a string, which would explain why the calculation failed and the string instead got concatenated 1000 times. ---
### Author: ![stecino](https://avatars.discourse-cdn.com/v4/letter/s/ea666f/32.png) [@stecino](https://discuss.elastic.co/u/stecino) #### Post date: [June 10, 2016, 7:25pm UTC](https://discuss.elastic.co/t/arithmetic-with-string/52131/5 "2016-06-10T19:25:03Z")
It's converted into float ---
### Author: ![stecino](https://avatars.discourse-cdn.com/v4/letter/s/ea666f/32.png) [@stecino](https://discuss.elastic.co/u/stecino) #### Post date: [June 10, 2016, 7:44pm UTC](https://discuss.elastic.co/t/arithmetic-with-string/52131/6 "2016-06-10T19:44:09Z")
Looks like adding the field and doing a convert in single mutate is the problem. I found on this [Convert String to float failed](https://discuss.elastic.co/t/convert-string-to-float-failed/32232) where someone was having the same type of issue. Ended up breaking up into to mutates mutate { add\_field =\> { "Test1"=\> "%{Test}" }} mutate { convert =\> {"Test1"=\> "float"} } This should be fixed. So the resulting calculation now is as expected ``` "Test1" => 5.34, "foo" => 5340.0 ``` } ---
### Author: ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system) #### Post date: [July 6, 2017, 4:53am UTC](https://discuss.elastic.co/t/arithmetic-with-string/52131/7 "2017-07-06T04:53:32Z")