Documentation

# contour3

3-D contour plot

## Syntax

``contour3(Z)``
``contour3(X,Y,Z)``
``contour3(___,levels)``
``contour3(___,LineSpec)``
``contour3(___,Name,Value)``
``contour3(ax,___)``
``M = contour3(___)``
``[M,c] = contour3(___)``

## Description

example

````contour3(Z)` creates a 3-D contour plot containing the isolines of matrix `Z`, where `Z` contains height values on the x-y plane. MATLAB® automatically selects the contour lines to display. The column and row indices of `Z` are the x and y coordinates in the plane, respectively.```

example

````contour3(X,Y,Z)` specifies the x and y coordinates for the values in `Z`.```

example

````contour3(___,levels)` specifies the contour lines to display as the last argument in any of the previous syntaxes. Specify `levels` as a scalar value `n` to display the contour lines at `n` automatically chosen levels (heights). To draw the contour lines at specific heights, specify `levels` as a vector of monotonically increasing values. To draw the contours at one height (`k`), specify `levels` as a two-element row vector `[k k]`.```
````contour3(___,LineSpec)` specifies the style and color of the contour lines.```
````contour3(___,Name,Value)` specifies additional options for the contour plot using one or more name-value pair arguments. Specify the options after all other input arguments. For a list of properties, see Contour Properties.```
````contour3(ax,___)` displays the contour plot in the target axes. Specify the axes as the first argument in any of the previous syntaxes.```
````M = contour3(___)` returns the contour matrix `M`, which contains the (x, y) coordinates of the vertices at each level.```

example

````[M,c] = contour3(___)` returns the contour matrix and the contour object `c`. Use `c` to set properties after displaying the contour plot.```

## Examples

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Define `Z` as a function of `X` and `Y`. In this case, call the `sphere` function to create `X`, `Y`, and `Z`. Then plot the contours of `Z`.

```[X,Y,Z] = sphere(50); contour3(X,Y,Z);``` Define `Z` as a function of two variables, `X` and `Y`. Then plot the contours of `Z`. In this case, let MATLAB® choose the contours and the limits for the x- and y-axes.

```[X,Y] = meshgrid(-5:0.25:5); Z = X.^2 + Y.^2; contour3(Z)``` Now specify `50` contour levels, and display the results within the x and y limits used to calculate `Z`.

`contour3(X,Y,Z,50)` Define `Z` as a function of two variables, `X` and `Y`. Then plot the contours at `Z = [-.2 -.1 .1 .2]`. Show the contour labels by setting the `ShowText` property to `'on'`.

```[X,Y] = meshgrid(-2:0.25:2); Z = X.*exp(-X.^2-Y.^2); contour3(X,Y,Z,[-.2 -.1 .1 .2],'ShowText','on')``` Define `Z` as a function of `X` and `Y`. In this case, call the `peaks` function to create `X`, `Y`, and `Z`. Then display the contours at `Z = 2`.

```[X,Y,Z] = peaks; contour3(X,Y,Z,[2 2]);``` Define `Z` as a function of two variables, `X` and `Y`. Plot 30 contours of `Z`, and then set the line width to `3`.

```[X,Y] = meshgrid(-2:0.0125:2); Z = X.*exp(-X.^2-Y.^2); [M,c] = contour3(X,Y,Z,30); c.LineWidth = 3;``` ## Input Arguments

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x-coordinates, specified as a matrix the same size as `Z`, or as a vector with length `n`, where `[m,n] = size(Z)`. The default value of `X` is the vector `(1:n)`.

When `X` is a matrix, the values must be strictly increasing or decreasing along one dimension and remain constant along the other dimension. The dimension that varies must be the opposite of the dimension that varies in `Y`. You can use the `meshgrid` function to create `X` and `Y` matrices.

When `X` is a vector, the values must be strictly increasing or decreasing.

Example: `X = 1:10`

Example: `X = [1 2 3; 1 2 3; 1 2 3]`

Example: `[X,Y] = meshgrid(1:10)`

The `XData` property of the `Contour` object stores the x-coordinates.

Data Types: `single` | `double` | `int8` | `int16` | `int32` | `int64` | `uint8` | `uint16` | `uint32` | `uint64`

y-coordinates, specified as a matrix the same size as `Z`, or as a vector with length `m`, where `[m,n] = size(Z)`. The default value of `Y` is the vector `(1:m)`.

When `Y` is a matrix, the values must be strictly increasing or decreasing along one dimension and remain constant along the other dimension. The dimension that varies must be the opposite of the dimension that varies in `X`. You can use the `meshgrid` function to create the `X` and `Y` matrices.

When `Y` is a vector, the values must be strictly increasing or decreasing.

Example: `Y = 1:10`

Example: `Y = [1 1 1; 2 2 2; 3 3 3]`

Example: `[X,Y] = meshgrid(1:10)`

The `YData` property of the `Contour` object stores the y-coordinates.

Data Types: `single` | `double` | `int8` | `int16` | `int32` | `int64` | `uint8` | `uint16` | `uint32` | `uint64`

z-coordinates, specified as a matrix. This matrix must have at least two rows and two columns, and it must contain at least two different values.

Example: `Z = peaks(20)`

The `ZData` property of the `Contour` object stores the z-coordinates.

Data Types: `single` | `double` | `int8` | `int16` | `int32` | `int64` | `uint8` | `uint16` | `uint32` | `uint64`

Contour levels, specified as a scalar whole number or a vector. Use this argument to control the number and location of the contour lines. When you do not specify the levels, the `contour3` function chooses the levels automatically.

• To draw contour lines at n automatically chosen heights, specify `levels` as the scalar value n.

• To draw the contour lines at specific heights, specify `levels` as a vector of monotonically increasing values.

• To draw contour lines at a single height `k`, specify `levels` as a two-element row vector ```[k k]```.

Example: `contour3(peaks,10)` draws contour lines at 10 automatically chosen heights on the `peaks` function.

Example: `contour3(peaks,[-4 0 4])` draws contour lines at 3 specific heights on the `peaks` function: `-4`, `0`, and `4`.

Example: `contour3(peaks,[3 3])` draws contour lines to show where the height of the `peaks` function is `3`.

Data Types: `single` | `double` | `int8` | `int16` | `int32` | `int64` | `uint8` | `uint16` | `uint32` | `uint64`

Line style and color, specified as a character vector or string scalar containing line style symbols, color options, or both. The line style symbols are listed in the following table, and they can appear in any order. Marker symbols such as `'o'` are ignored.

You do not need to specify both the line style and the color. For example, if you omit the line style and specify the color, then the plot shows solid lines using the specified color.

Line StyleDescriptionResulting Line
`-`Solid line (default) `--`Dashed line `:`Dotted line `-.`Dash-dot line This table lists the available color options.

OptionDescriptionEquivalent RGB Triplet
`'red'` or `'r'`Red`[1 0 0]`
`'green'` or `'g'`Green`[0 1 0]`
`'blue'` or `'b'`Blue`[0 0 1]`
`'yellow'` or `'y'`Yellow`[1 1 0]`
`'magenta'` or `'m'`Magenta`[1 0 1]`
`'cyan'` or `'c'`Cyan`[0 1 1]`
`'white'` or `'w'`White`[1 1 1]`
`'black'` or `'k'`Black`[0 0 0]`

Target axes, specified as an `Axes` object. If you do not specify the axes, then `contour3` plots into the current axes.

### Name-Value Pair Arguments

Specify optional comma-separated pairs of `Name,Value` arguments. `Name` is the argument name and `Value` is the corresponding value. `Name` must appear inside quotes. You can specify several name and value pair arguments in any order as `Name1,Value1,...,NameN,ValueN`.

Example: `contour3(Z,'ShowText','on')` displays the contour line labels.

### Note

The properties listed here are only a subset. For a complete list, see Contour Properties.

Contour line labels, specified as one of these values:

• `'off'` — Do not label the contour lines.

• `'on'` — Display the height values along the contour lines.

Contour line width, specified as a positive value in points. One point equals 1/72 inch.

Label spacing along the contour lines, specified as a scalar value in points, where one point is 1/72 inch. Use this property to control the number of contour labels along the contour lines. Smaller values produce more labels.

You must set the `ShowText` property to `'on'` for the `LabelSpacing` property to have an effect.

If you use the `clabel` function to display the labels, then the `LabelSpacing` property has no effect and the plot displays one label per line.

## Output Arguments

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Contour matrix, returned as two-row matrix. This matrix contains the contour levels (heights) and the coordinates of the vertices at each level. The data is arranged sequentially in n sets of columns for n contour lines:

• The first column in each set contains the contour level and the number of vertices at that level. The top number is the contour level, and the bottom number is the number of vertices.

• Subsequent columns in the set are the (x, y) coordinates of the vertices. Each column represents an ordered pair. The top number is the x-coordinate, and the bottom number is the y-coordinate.

For example, here are the first few columns of the contour matrix ```M = contour(peaks(3))```: The `ContourMatrix` property of the `Contour` object stores the contour matrix.

`Contour` object. Use this object to set properties after displaying the contour plot.