# CoefficientAssignment Properties

Coefficient assignments

A `CoefficientAssignment` object contains a description of the PDE coefficients. A `PDEModel` container has a vector of `CoefficientAssignment` objects in its `EquationCoefficients.CoefficientAssignments` property.

Coefficients are the m, d, c, a, and f variables in the PDE

`$m\frac{{\partial }^{2}u}{\partial {t}^{2}}+d\frac{\partial u}{\partial t}-\nabla ·\left(c\nabla u\right)+au=f$`

or the eigenvalue problem

`$\begin{array}{l}-\nabla ·\left(c\nabla u\right)+au=\lambda du\\ \text{or}\\ -\nabla ·\left(c\nabla u\right)+au={\lambda }^{2}mu\end{array}$`

Create coefficients for your model using the `specifyCoefficients` function.

## Properties

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Region type, returned as `'face'` for a 2-D region, or `'cell'` for a 3-D region.

Data Types: `char` | `string`

Region ID, returned as a vector of positive integers. To determine which ID corresponds to which portion of the geometry, use the `pdegplot` function. Set the `'FaceLabels'` name-value pair to `'on'`.

Data Types: `double`

Second-order time derivative coefficient, returned as a scalar, column vector, or function handle. For details of the `m` coefficient specification, see m, d, or a Coefficient for specifyCoefficients.

Data Types: `double` | `function_handle`
Complex Number Support: Yes

First-order time derivative coefficient, returned as a scalar, column vector, or function handle. For details of the `d` coefficient specification, see m, d, or a Coefficient for specifyCoefficients.

Data Types: `double` | `function_handle`
Complex Number Support: Yes

Second-order space derivative coefficient, returned as a scalar, column vector, or function handle. For details of the `c` coefficient specification, see c Coefficient for specifyCoefficients.

Data Types: `double` | `function_handle`
Complex Number Support: Yes

Solution multiplier coefficient, returned as a scalar, column vector, or function handle. For details of the `a` coefficient specification, see m, d, or a Coefficient for specifyCoefficients.

Data Types: `double` | `function_handle`
Complex Number Support: Yes

Source coefficient, returned as a scalar, column vector, or function handle. For details of the `f` coefficient specification, see f Coefficient for specifyCoefficients.

Data Types: `double` | `function_handle`
Complex Number Support: Yes