# Plot Polar Equations in an App

You can plot a polar equation in an app using the `polaraxes` and `polarplot` functions. In this example app, when an app user changes parameter values or component properties, the polar plot updates to reflect the changes. This example demonstrates these app building tasks:

• Create different types of axes programmatically to display plots that `uiaxes` does not support.

• Call a plotting function within an app.

### Set Up Polar Axes

You can add specialized axes to an app programmatically. This approach is useful because the `UIAxes` object supports only Cartesian plots. For example, polar axes are a specialized type of axes for plotting polar coordinates. Unlike `UIAxes` objects, which you can add to your app interactively, you must create a `PolarAxes` object within a startupFcn callback function. In your `startupFcn` code, create and position the polar axes within the app. Store the `PolarAxes` object in a new private property named `Pax` so that you can access it in different parts of the app code. You can create a private property by selecting Property from the Editor tab of the App Designer toolstrip and choosing the Private Property option.

```app.Pax = polaraxes(app.UIFigure); app.Pax.Units = "pixels"; app.Pax.Position = [260 55 230 230]; ```

For more information about `startupFcn` callbacks, see Startup Tasks and Input Arguments in App Designer.

### Plot Polar Equation

Plot a polar equation by specifying the `app.Pax` property you created as the first input to the `polarplot` function. For example, to update the plot when an app user changes parameter values, create a `ValueChangedFcn` callback function for the a and b edit fields. Then add the plotting command within this callback.

```theta = 0:pi/1800:2*pi; r = (1 + sin(a.*theta)).^(1/b); plotline = polarplot(app.Pax,theta,r); ```