# How to use Math operations in actions with ctx.payload.\* **URL:** \ **Category:** Elasticsearch\ **Tags:** elastic-stack-alerting\ **Created:** [October 23, 2018, 7:42pm UTC](https://discuss.elastic.co/t/how-to-use-math-operations-in-actions-with-ctx-payload/153673 "2018-10-23T19:42:42Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![shiv94](https://avatars.discourse-cdn.com/v4/letter/s/bc8723/32.png) [@shiv94](https://discuss.elastic.co/u/shiv94)\ **Post date:** [October 23, 2018, 7:42pm UTC](https://discuss.elastic.co/t/how-to-use-math-operations-in-actions-with-ctx-payload/153673/1 "2018-10-23T19:42:42Z")
Hey, how do I use math operations like multiplication (_) in actions with ctx.payload._ for example, {{#..}}{{\_source.system.filesystem.used.pct}}{{/..}} gives value 0.7 but I want 0.7\*100 = 70 and also how do I convert bytes to gb or mb. {{#..}}{{\_source.system.memory.total}}{{/..}} value is 38114820096 bytes. How do I get required format? ---
**Author:** ![spinscale](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/spinscale/32/25011_2.png) [@spinscale](https://discuss.elastic.co/u/spinscale)\ **Post date:** [October 24, 2018, 7:35am UTC](https://discuss.elastic.co/t/how-to-use-math-operations-in-actions-with-ctx-payload/153673/2 "2018-10-24T07:35:42Z")
You cannot do those calculation within mustache. You have to `transform` the data using a script first and then access this data in your mustache template. See [https://www.elastic.co/guide/en/elastic-stack-overview/6.4/transform-script.html](https://www.elastic.co/guide/en/elastic-stack-overview/6.4/transform-script.html) ---
**Author:** ![shiv94](https://avatars.discourse-cdn.com/v4/letter/s/bc8723/32.png) [@shiv94](https://discuss.elastic.co/u/shiv94)\ **Post date:** [October 24, 2018, 1:21pm UTC](https://discuss.elastic.co/t/how-to-use-math-operations-in-actions-with-ctx-payload/153673/3 "2018-10-24T13:21:23Z")
"transform": { "script": { "source" : "doc['\_source.system.filesystem.used.pct'] \* multiplier", "params": { "multiplier": 100 } } } How do I use this array field {{ctx.payload.aggregations.host.buckets}}{{top\_hit.hits.hits}}{{\_source.system.filesystem.used.pct}}? ---
**Author:** ![spinscale](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/spinscale/32/25011_2.png) [@spinscale](https://discuss.elastic.co/u/spinscale)\ **Post date:** [October 24, 2018, 1:52pm UTC](https://discuss.elastic.co/t/how-to-use-math-operations-in-actions-with-ctx-payload/153673/4 "2018-10-24T13:52:04Z")
see [https://www.elastic.co/guide/en/elastic-stack-overview/6.4/transform.html](https://www.elastic.co/guide/en/elastic-stack-overview/6.4/transform.html) be aware that a transform **replaces** the existing payload, so if you want to have access to the existing fields, you have to return those plus the newly added ones. See [https://github.com/elastic/examples/tree/master/Alerting](https://github.com/elastic/examples/tree/master/Alerting) for a couple of examples ---
**Author:** ![shiv94](https://avatars.discourse-cdn.com/v4/letter/s/bc8723/32.png) [@shiv94](https://discuss.elastic.co/u/shiv94)\ **Post date:** [October 24, 2018, 2:37pm UTC](https://discuss.elastic.co/t/how-to-use-math-operations-in-actions-with-ctx-payload/153673/5 "2018-10-24T14:37:15Z")
This information helpful to me. How do I use array field like this {{#ctx.payload.aggregations.host.buckets}}{{#top\_hit.hits.hits}}{{\_source.system.filesystem.used.pct}} in source field. If I use "source" : "doc['\_source.system.filesystem.used.pct'] \* multiplier", it throws a runtime error. I cannot access \_source.system.filesystem.used.pct field directly because its object in a array ---
**Author:** ![shiv94](https://avatars.discourse-cdn.com/v4/letter/s/bc8723/32.png) [@shiv94](https://discuss.elastic.co/u/shiv94)\ **Post date:** [October 24, 2018, 4:41pm UTC](https://discuss.elastic.co/t/how-to-use-math-operations-in-actions-with-ctx-payload/153673/6 "2018-10-24T16:41:30Z")
"transform": { "script": { "source": "doc['\_source.system.filesystem.used.pct'] \* params.multiplier", "lang": "painless", "params": { "multiplier": 100 } } } I am getting runtime error ![image](https://us1.discourse-cdn.com/elastic/original/3X/d/8/d896076bb26a1e347d90e88fab72da34e05c9801.png) "payload": { "\_shards": { "total": 130, "failed": 0, "successful": 130, "skipped": 125 }, "hits": { "hits": , "total": 35, "max\_score": 0 }, "took": 32, "timed\_out": false, "aggregations": { "host": { "doc\_count\_error\_upper\_bound": 0, "sum\_other\_doc\_count": 0, "buckets": [ { "doc\_count": 5, "top\_hit": { "hits": { "hits": [ { "\_index": "metricbeat-6.4.1-2018.10.24", "\_type": "doc", "\_source": { "@timestamp": "2018-10-24T18:14:02.128Z", "system": { "filesystem": { "device\_name": "xxx", "total": xxx, "mount\_point": "/", "free\_files": xxx, "available": xxx, "files": xxx, "used": { "pct": 0.6516, "bytes": 12685934592 ..... ..... } ---
**Author:** ![spinscale](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/spinscale/32/25011_2.png) [@spinscale](https://discuss.elastic.co/u/spinscale)\ **Post date:** [October 25, 2018, 6:40am UTC](https://discuss.elastic.co/t/how-to-use-math-operations-in-actions-with-ctx-payload/153673/7 "2018-10-25T06:40:24Z")
the `doc` notation is not applicate for watcher, it is only used when you want to access doc values in a query. Also, you need to access an array of data, namely `ctx.payload.hits.hits`, which contains the hits of a search response, and each hit has a `_source`, so you need to access this array via a for loop. Please have a look at the examples I posted before. ---
**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\ **Post date:** [November 22, 2018, 1:46pm UTC](https://discuss.elastic.co/t/how-to-use-math-operations-in-actions-with-ctx-payload/153673/9 "2018-11-22T13:46:08Z")
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