# getStiffValues

> Stiff diagram values in meq/L: Na⁺ + K⁺, Ca²⁺, Mg²⁺ (cations) and Cl⁻, HCO₃⁻ + CO₃²⁻ (falling back to alkalinitytotalascaco3), SO₄²⁻ (anions). Unmeasured ions count as 0. Returns undefined without at least one of those cations and one of those anions measured.

> **getStiffValues**(`sample`): [`StiffValues`](/utils/api/type-aliases/StiffValues) \| `undefined`

Stiff diagram values in meq/L: Na⁺ + K⁺, Ca²⁺, Mg²⁺ (cations) and Cl⁻,
HCO₃⁻ + CO₃²⁻ (falling back to `alkalinity_total_as_caco3`), SO₄²⁻
(anions). Unmeasured ions count as 0. Returns `undefined` without at least
one of those cations and one of those anions measured.

## Parameters

### sample

`WaterSample`

## Returns

[`StiffValues`](/utils/api/type-aliases/StiffValues) \| `undefined`