MATLAB Function Reference |

Evaluate the solution of a differential equation

**Syntax**

sxint = deval(sol,xint) sxint = deval(xint,sol) sxint = deval(sol,xint,idx) sxint = deval(xint,sol,idx) [sxint, spxint] = deval(...)

**Description**

```
sxint = deval(sol,xint) and sxint = deval(xint,sol)
```

evaluate the solution of a differential equation problem. `sol`

is a structure returned by one of these solvers:

- An initial value problem solver (
`ode45`

,`ode23`

,`ode113`

,`ode15s`

,`ode23s`

,`ode23t`

,`ode23tb`

,`ode15i`

) - The delay differential equations solver (
`dde23`

), - The boundary value problem solver (
`bvp4c`

).

`xint`

is a point or a vector of points at which you want the solution. The elements of `xint`

must be in the interval `[sol.x(1),sol.x(end)]`

. For each `i`

, `sxint(:,i)`

is the solution at `xint(i)`

.

```
sxint = deval(sol,xint,idx) and sxint = deval(xint,sol,idx)
```

evaluate as above but return only the solution components with indices listed in the vector `idx`

.

`[sxint, spxint] = deval(...)`

also returns `spxint`

, the value of the first derivative of the polynomial interpolating the solution.

**Example**

This example solves the system using `ode45`

, and evaluates and plots the first component of the solution at 100 points in the interval `[0,20]`

.

**See Also**

ODE solvers: `ode45`

, `ode23`

, `ode113`

, `ode15s`

, `ode23s`

, `ode23t`

, `ode23tb`

, `ode15i`

DDE solver: `dde23`

BVP solver: `bvp4c`

detrend | diag |

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