# TDIGEST.BYREVRANK

```json metadata
{
  "title": "TDIGEST.BYREVRANK",
  "description": "Returns, for each input reverse rank, an estimation of the floating-point value with that reverse rank",
  "categories": ["docs","develop","stack","oss","rs","rc","oss","kubernetes","clients"],
  "arguments": [{"name":"key","type":"key"},{"multiple":true,"name":"reverse_rank","type":"double"}],
  "syntax_fmt": "TDIGEST.BYREVRANK key reverse_rank [reverse_rank ...]",
  "complexity": "O(1)",
  "group": "tdigest",
  "acl_categories": ["@tdigest","@read"],
  "since": "2.4.0",
  "tableOfContents": {"sections":[{"id":"required-arguments","title":"Required arguments"},{"id":"examples","title":"Examples"},{"id":"redis-enterprise-and-redis-cloud-compatibility","title":"Redis Enterprise and Redis Cloud compatibility"},{"id":"return-information","title":"Return information"}]}
}
```













Returns, for each input reverse rank (`revrank`), an estimation of the floating-point value with that reverse rank.
Multiple estimations can be retrieved in a single call.

## Required arguments

<details open><summary><code>key</code></summary>

is the key name of an existing t-digest sketch.
</details>

<details open><summary><code>revrank</code></summary>

Reverse ranks for which the values should be retrieved.

0 is the reverse rank of the value of the largest observation.
  
_n_-1 is the reverse rank of the value of the smallest observation, where _n_ denotes the number of observations added to the sketch.
</details>

## Examples


redis> TDIGEST.CREATE t COMPRESSION 1000
OK
redis> TDIGEST.ADD t 1 2 2 3 3 3 4 4 4 4 5 5 5 5 5
OK
redis> TDIGEST.BYREVRANK t 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
 1) "5"
 2) "5"
 3) "5"
 4) "5"
 5) "5"
 6) "4"
 7) "4"
 8) "4"
 9) "4"
10) "3"
11) "3"
12) "3"
13) "2"
14) "2"
15) "1"
16) "-inf"


## Redis Enterprise and Redis Cloud compatibility

| Redis<br />Enterprise | Redis<br />Cloud | <span style="min-width: 9em; display: table-cell">Notes</span> |
|:----------------------|:-----------------|:------|
| <span title="Supported">&#x2705; Supported</span><br /> | <span title="Supported"><nobr>&#x2705; Flexible & Annual</nobr></span><br /><span title="Supported">&#x2705; Free & Fixed</nobr></span> |  |

## Return information

{{< multitabs id="tdigest-byrevrank-return-info" 
    tab1="RESP2" 
    tab2="RESP3" >}}

One of the following:

* [Array](https://redis.io/docs/latest/develop/reference/protocol-spec#arrays) of [bulk strings](https://redis.io/docs/latest/develop/reference/protocol-spec#bulk-strings) as floating-points, populated with value_1, value_2, ..., value_R:
    * an accurate result when `rank` is `0`, the value of the largest observation.
    * an accurate result when `rank` is _n_-1, the value of the smallest observation, where _n_ denotes the number of observations added to the sketch.
    * `inf` when `rank` is equal to _n_ or larger than _n_.
    * `nan` for all ranks when the given sketch is empty.
* [Simple error reply](https://redis.io/docs/latest/develop/reference/protocol-spec#simple-errors) in these cases: the given key does not exist or is of an incorrect type, rank parsing errors, or an incorrect number of arguments.

-tab-sep-

One of the following:

* [Array](https://redis.io/docs/latest/develop/reference/protocol-spec#arrays) of [doubles](https://redis.io/docs/latest/develop/reference/protocol-spec#doubles) as floating-points, populated with value_1, value_2, ..., value_R:
    * an accurate result when `rank` is `0`, the value of the largest observation.
    * an accurate result when `rank` is _n_-1, the value of the smallest observation, where _n_ denotes the number of observations added to the sketch.
    * `inf` when `rank` is equal to _n_ or larger than _n_.
    * `nan` for all ranks when the given sketch is empty.
* [Simple error reply](https://redis.io/docs/latest/develop/reference/protocol-spec#simple-errors) in these cases: the given key does not exist or is of an incorrect type, rank parsing errors, or an incorrect number of arguments.