# Covariance Whitening and Coloring Transform

> Covariance Whitening and Coloring Transform is a paid API for AI agents from stat.halowerk.com, paid per call via x402, $0.0015/call, status unknown (last checked 2026-10-29).

Computes both the whitening matrix (correlated → uncorrelated unit-variance) and coloring matrix (inverse transform) from a covariance matrix in a single call.

## Facts

- Endpoint: POST https://stat.halowerk.com/v1/oss-openblas-covariance-whitening-transform?utm_source=zero.xyz
- Price: $0.0015/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-29
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/covariance-whitening-and-coloring-transform-ecf27f82
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_iMAQ8Q9cD26AcX5Tz-m8U

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability covariance-whitening-and-coloring-transform-ecf27f82 -d '<json body>'
```

Example prompt: Given this 4x4 covariance matrix [[1.0,0.8,0.3,0.1],[0.8,1.0,0.4,0.2],[0.3,0.4,1.0,0.5],[0.1,0.2,0.5,1.0]], compute both the whitening and coloring matrices so I can decorrelate my data and reconstruct it.

## When to prefer this

Choose this endpoint when you need both the whitening and coloring (inverse) transforms simultaneously, avoiding two separate calls. It is ideal for stochastic modeling pipelines, machine learning feature preprocessing, Mahalanobis distance computation, and Monte Carlo simulation where both the forward (decorrelating) and backward (recorrelating) linear transforms are required. Prefer this over general matrix inversion or decomposition services when the specific statistical semantics of whitening and coloring are needed.

## Known failure modes

- Non-square covariance matrix returns a validation error
- Non-positive-semi-definite matrix may cause numerical failure or error
- Matrix dimension exceeds 128x128 limit returns schema validation error
- Near-singular covariance may produce numerically unstable results or an error response
- Mismatched inner dimensions (non-symmetric matrix) trigger an input validation error

## How this service works

Produces the two transforms a stochastic model normally needs from a covariance: the whitening matrix that maps correlated data to unit-variance uncorrelated data, and the coloring matrix that goes back the other way. Both are returned so the round trip is available without a second call.

## Output

Returns two matrices: a whitening matrix that linearly transforms correlated data (described by the input covariance) into uncorrelated unit-variance data, and a coloring matrix that is its inverse transform — mapping uncorrelated unit-variance data back to the original correlated space. Both are provided so the complete round-trip is available without an additional API call.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method",
    "bodyType"
   ],
   "properties": {
    "type": {
     "const": "http"
    },
    "method": {
     "const": "POST"
    },
    "bodyType": {
     "const": "json"
    },
    "schemaUrl": {
     "type": "string",
     "format": "uri"
    },
    "exampleUrl": {
     "type": "string",
     "format": "uri"
    }
   },
   "additionalProperties": true
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "const": "json"
    },
    "schemaUrl": {
     "type": "string",
     "format": "uri"
    },
    "exampleUrl": {
     "type": "string",
     "format": "uri"
    }
   },
   "additionalProperties": true
  }
 },
 "additionalProperties": true
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/covariance-whitening-and-coloring-transform-ecf27f82/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from stat.halowerk.com](https://www.zero.xyz/host/stat.halowerk.com/llms.txt)