# Calculating new fields using ruby filter

**URL:** https://discuss.elastic.co/t/calculating-new-fields-using-ruby-filter/237163
**Category:** Logstash
**Created:** [June 15, 2020, 3:49pm UTC](https://discuss.elastic.co/t/calculating-new-fields-using-ruby-filter/237163 "2020-06-15T15:49:46Z")
**Posts on this page:** 1
**Showing post:** 2

<div class="post-metadata">

### Author: ![Badger](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/badger/32/25190_2.png) [@Badger](https://discuss.elastic.co/u/Badger)
#### Post date: [June 15, 2020, 5:18pm UTC](https://discuss.elastic.co/t/calculating-new-fields-using-ruby-filter/237163/2 "2020-06-15T17:18:03Z")

</div>

> [@inchirah](#):
>
> `if(["Contrainte"] >= -78){`

That is comparing an array of strings with a number. logstash does not handle that well.

Note that if you fix it to compare the field called Contrainte

```
if [Contrainte] >= -78 {

```

then you will [still](https://discuss.elastic.co/t/comparing-number-in-conditionnal-event-treatement/217043/5) get an exception if the field does not exist.

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