# Contours

Contours of an implicit function

## Value Summary

 Mandatory List of arithmetical expressions

## Graphics Primitives

ObjectsContours Default Values
`plot::Implicit2d`, `plot::Implicit3d`[`0`]

## Description

With `Contours`, you can set the contour(s) of an implicit function.

By default, `plot::Implicit2d` and `plot::Implicit3d` plot the set . Using `Contours`, you can instead plot the set for any real c or for a sequence of such values.

## Examples

### Example 1

The following command plots a series of cuts through a sphere:

```plot(plot::Implicit2d(x^2 + y^2, x = -1..1, y = -1..1, Contours = [0, 0.25^2, 0.5^2, 0.75^2, 1.0])):```

### Example 2

Being an expression attribute, `Contours` can be animated:

```plot(plot::Implicit2d(x^2-y^2, x = -1..1, y = -1..1, Contours = [1/2*cos(a)], a = 0..2*PI)):```

### Example 3

The contour currently plotted is passed to the color functions and can be used to distinguish them visually:

```plot( plot::Implicit3d(x^y - y*z, x = 1..4, y = 1..4, z = -2..2, Contours = [\$0..5], FillColorFunction = ((x,y,z,dx,dy,dz,c) -> RGB::ColorList[round(c)+1])) )```