# requirements pack

6 nodes, in `noodlelab` and above.

## Requirements

(node-requirements.check_candidates)=
### Check Candidates

`requirements.check_candidates`

Score candidate designs, one per row, against the requirements whose
quantity is a column of the table. Adds a ``<ID> margin`` column for
each, and ``compliant``: whether the row meets them all. ``compliant``
(the output) keeps only those rows, ready to sort and pick from.

**Inputs**

| Name | Type | Description |
|---|---|---|
| `table` | `DataFrame` |  |
| `requirements` | `RequirementSet` |  |
| `only` | `str` | Requirement IDs to apply, comma-separated; empty: all Default `''`. |

**Outputs**

| Name | Type | Description |
|---|---|---|
| `table` | `DataFrame` |  |
| `compliant` | `DataFrame` |  |

(node-requirements.load_requirements)=
### Load Requirements

`requirements.load_requirements`

Read requirements from a specification file: a CSV (or a YAML or JSON
list) with the columns id, quantity, op, limit and optionally unit, upper,
tolerance, text, method, priority and parent.

**Inputs**

| Name | Type | Description |
|---|---|---|
| `path` | `FileRef` |  |

**Outputs**

| Name | Type | Description |
|---|---|---|
| `result` | `RequirementSet` |  |

(node-requirements.merge_requirements)=
### Merge Requirements

`requirements.merge_requirements`

One set from two, such as system and subsystem requirements. An ID may
appear only once.

**Inputs**

| Name | Type | Description |
|---|---|---|
| `a` | `RequirementSet` |  |
| `b` | `RequirementSet` |  |

**Outputs**

| Name | Type | Description |
|---|---|---|
| `result` | `RequirementSet` |  |

(node-requirements.requirement_value)=
### Requirement Value

`requirements.requirement_value`

A requirement's limit, to design with: a quantity when it has a unit
(for a range, the lower limit). The required data rate, say, sets the
bandwidth the link needs.

**Inputs**

| Name | Type | Description |
|---|---|---|
| `requirements` | `RequirementSet` |  |
| `id` | `str` | Which requirement Default `''`. |

**Outputs**

| Name | Type | Description |
|---|---|---|
| `result` | `Any` |  |

(node-requirements.requirements)=
### Requirements

`requirements.requirements`

Write down what the design must achieve, one requirement per line:

**Inputs**

| Name | Type | Description |
|---|---|---|
| `text` | `str` | One per line: ID quantity >= limit unit [method] # statement. Also <=, > and < (strict), == limit ± tolerance, between low and high Default `'REQ-001 margin >= 3 dB  # The design shall have 3 dB of margin'`. |

**Outputs**

| Name | Type | Description |
|---|---|---|
| `result` | `RequirementSet` |  |

(node-requirements.verify_requirement)=
### Verify Requirement

`requirements.verify_requirement`

Check a result against a requirement. The check passes when the value
is within the limit (every element of an array: the margin is then the
worst case) and reports the margin, how far inside the limit it is in
the requirement's unit. A failed requirement does not stop the run: it
marks the node, is listed in the Problems tab and fails ``noodlelab
test``. Chain ``log`` from node to node and put it in a report with Add
Compliance Matrix.

**Inputs**

| Name | Type | Description |
|---|---|---|
| `requirements` | `RequirementSet` |  |
| `value` | `Any` |  |
| `id` | `str` | Which requirement Default `''`. |
| `log` | `Verifications \| None` | Earlier verifications: chain these nodes into one matrix Optional. |

**Outputs**

| Name | Type | Description |
|---|---|---|
| `value` | `Any` |  |
| `check` | `Check` |  |
| `log` | `Verifications` |  |