# Slot: covariance 


_Covariance of the unit-intensity noise increment across the axis named by `correlated_over` — the second-order structure of the driving process, stated as mathematics rather than as a factorisation. Must be square in that axis, symmetric and positive semi-definite; its diagonal carries per-element variances and need NOT be unity, so unequal variances and cross-element correlation are expressed together. The realised increment is the declared sigma times a draw from this covariance, so `parameters: {sigma: ...}` continues to mean what it means for uncorrelated noise. Absent (the default) means the increment is independent across that axis. Being a `Parameter`, it carries the full provenance triple: a literal `value:`, existing bytes via `source:`+`measure:`, or — the usual case for a derived operator — `producer:`, whose FunctionCall records how the structure was obtained (projecting a spatially white field into a modal basis, spreading independent per-region drives through a connectome). The generative account therefore lives in the provenance, and the matrix itself stays a statement about the process. How a backend samples it (Cholesky, eigendecomposition, whitening) is a backend concern and is never stated here._



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URI: [tvbo:slot/covariance](https://w3id.org/tvbo/slot/covariance)
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## Applicable Classes

| Name | Description | Modifies Slot |
| --- | --- | --- |
| [Noise](../classes/Noise.qmd) |  |  no  |






## Properties

### Type and Range

| Property | Value |
| --- | --- |
| Range | [Parameter](../classes/Parameter.qmd) |
| Domain Of | [Noise](../classes/Noise.qmd) |

### Cardinality and Requirements

| Property | Value |
| --- | --- |
### Slot Characteristics

| Property | Value |
| --- | --- |
| Owner | [Noise](../classes/Noise.qmd) |












## Identifier and Mapping Information





### Schema Source


* from schema: https://w3id.org/tvbo




## Mappings

| Mapping Type | Mapped Value |
| ---  | ---  |
| self | tvbo:covariance |
| native | tvbo:covariance |




## LinkML Source

<details>
```yaml
name: covariance
description: 'Covariance of the unit-intensity noise increment across the axis named
  by `correlated_over` — the second-order structure of the driving process, stated
  as mathematics rather than as a factorisation. Must be square in that axis, symmetric
  and positive semi-definite; its diagonal carries per-element variances and need
  NOT be unity, so unequal variances and cross-element correlation are expressed together.
  The realised increment is the declared sigma times a draw from this covariance,
  so `parameters: {sigma: ...}` continues to mean what it means for uncorrelated noise.
  Absent (the default) means the increment is independent across that axis. Being
  a `Parameter`, it carries the full provenance triple: a literal `value:`, existing
  bytes via `source:`+`measure:`, or — the usual case for a derived operator — `producer:`,
  whose FunctionCall records how the structure was obtained (projecting a spatially
  white field into a modal basis, spreading independent per-region drives through
  a connectome). The generative account therefore lives in the provenance, and the
  matrix itself stays a statement about the process. How a backend samples it (Cholesky,
  eigendecomposition, whitening) is a backend concern and is never stated here.'
from_schema: https://w3id.org/tvbo
rank: 1000
owner: Noise
domain_of:
- Noise
range: Parameter
required: false
inlined: true

```
</details></div>