How can I build verticalBar chart based on some custom calculation

Thanks Wylie.

I am going with the TSVB option by following the initial steps mentioned in Filter ratio in TSVB.

I am trying to perform a sum operation on one of the fields but I do not see that field as an option. I used python to create mapping and later dumping the data using the API.

 "mappings": {
            "properties": {
                "timestamp": {
                    "type": "date"
                },
                "status": {
                    "type": "text",
                    "fields": {
                        "raw": {
                            "type": "keyword"
                        }
                    }
                },
                "service": {
                    "type": "text",
                    "fields": {
                        "raw": {
                            "type": "keyword"
                        }
                    }
                }
            }
        }

I can only see epoch_time in the dropdown. Is it because that's the only integer field? How would I make a sum aggregation on a string field like 'service'. Is my mapping correct?