peaks

Peaks function

Syntax

Z = peaks

Z = peaks(n)

Z = peaks(Xm,Ym)

[X,Y,Z] = peaks(___)

peaks(___)

Description

Return Coordinates

Z = peaks returns the z-coordinates of the peaks function evaluated over a 49-by-49 grid.

Z = peaks(n) returns the peaks function evaluated over an n-by-n grid. If you specify n as a vector of length k, MATLAB^® evaluates the function over a k-by-k grid.

Z = peaks(Xm,Ym) returns the peaks function evaluated at the points specified by Xm and Ym. The sizes of Xm and Ym must be the same or be compatible. For example, you can specify Xm and Ym as matrices in meshgrid format.

[X,Y,Z] = peaks(___) returns the x-, y-, and z-coordinates of the peaks function.

Create Surface Plot

peaks(___) plots the peaks function as a three-dimensional surface plot. You can use any of the input argument combinations in the previous syntaxes.

Examples

Plot Peaks Surface

Create a 5-by-5 matrix of peaks and display the surface.

figure
peaks(5)

 
z =  3*(1-x).^2.*exp(-(x.^2) - (y+1).^2) ... 
   - 10*(x/5 - x.^3 - y.^5).*exp(-x.^2-y.^2) ... 
   - 1/3*exp(-(x+1).^2 - y.^2) 
 

Plot at Points from Vector

Evaluate the peaks function over a 2-D grid that is defined by uniformly spaced values in the interval [-1,1].

n = -1:0.25:1;
Z = peaks(n)

Z = 9×9

    1.8559    2.4537    2.2247    0.9965   -0.7239   -2.0151   -2.2222   -1.4251   -0.2729
    1.7829    3.0862    3.6265    2.9423    1.3962   -0.0048   -0.4134    0.2037    1.1760
    0.7969    2.4879    3.5507    3.3044    1.9975    0.7001    0.3896    1.1388    2.1978
   -0.5659    1.2281    2.5614    2.6254    1.5850    0.5256    0.4756    1.4962    2.7556
   -1.6523    0.0636    1.4796    1.7530    0.9810    0.1904    0.3744    1.5728    2.9369
   -2.1491   -0.6469    0.6823    1.0566    0.5228   -0.0281    0.2795    1.4682    2.7624
   -1.9968   -0.7599    0.3898    0.7963    0.4641    0.0898    0.3754    1.3442    2.3768
   -1.1629   -0.0458    1.0400    1.5519    1.4226    1.1205    1.1713    1.6492    2.1708
    0.2289    1.5069    2.7942    3.5855    3.6886    3.3404    2.9344    2.6622    2.4338

Use the calculated values to create a three-dimensional surface plot.

surf(Z)

Plot at Points from 2-D Grid

Create 2-D grid coordinates with x-coordinates defined by the vector x and y-coordinates defined by the vector y.

x = -2:0.5:2;
y = 1:0.2:2;
[X,Y] = meshgrid(x,y);

Evaluate the peaks function over the 2-D grid.

Z = peaks(X,Y)

Z = 6×9

   -0.4808   -0.8639    0.2289    2.7942    3.6886    2.9344    2.4338    1.5813    0.5805
   -0.2470   -0.1924    1.4275    4.5254    5.8902    4.6339    2.8647    1.3897    0.4382
   -0.0730    0.3116    2.3394    5.8525    7.5679    5.9243    3.2006    1.2552    0.3350
    0.0320    0.5860    2.7339    6.2839    8.1000    6.3260    3.2091    1.1050    0.2561
    0.0764    0.6437    2.5958    5.7476    7.3967    5.7698    2.8374    0.9069    0.1901
    0.0797    0.5539    2.0967    4.5569    5.8591    4.5675    2.2099    0.6771    0.1328

Use the calculated values to create a three-dimensional surface plot.

surf(Z)

Return Coordinates Separately and Plot

Use the peaks function to create three matrices of the same size. Then, plot them as a mesh plot.

[X,Y,Z] = peaks(25);
mesh(X,Y,Z)

Input Arguments

n — Value representing 2-D grid

scalar | vector

Value representing a 2-D grid used to evaluate the function, specified as a scalar or vector.

• If n is a scalar, MATLAB creates the grid as [X,Y] = meshgrid(linspace(-3,3,n)). The value of n must be an integer greater than 1.

• If n is a vector, MATLAB creates the grid as [X,Y] = meshgrid(n). The elements of n must be double-precision numbers.

For example, Z = peaks(5) is the same as using this code.

[X,Y] = meshgrid(linspace(-3,3,5));
Z = peaks(X,Y)

Example: n = 5

Example: n = -2:0.1:2

Xm — x-coordinates of points

scalar | vector | matrix

x-coordinates of points, specified as a scalar, vector, or matrix. The sizes of Xm and Ym must be the same or be compatible. You can use the meshgrid function to create Xm and Ym. See Compatible Array Sizes for Basic Operations for more information about compatible arrays.

Example: Xm = [1 2 3; 1 2 3; 1 2 3]

Example: [Xm,Ym] = meshgrid(-5:0.5:5)

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

Ym — y-coordinates of points

scalar | vector | matrix

y-coordinates of points, specified as a scalar, vector, or matrix. The sizes of Xm and Ym must be the same or be compatible. You can use the meshgrid function to create Xm and Ym. See Compatible Array Sizes for Basic Operations for more information about compatible arrays.

Example: Ym = [1 1 1; 2 2 2; 3 3 3]

Example: [Xm,Ym] = meshgrid(-5:0.5:5)

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

Output Arguments

X — x-coordinates of points

scalar | vector | matrix

x-coordinates of points, returned as a scalar, vector, or matrix. If peaks is called with the Xm and Ym input arguments, then X is equal to Xm. Otherwise, X is a matrix that specifies the x-coordinates over a grid used for evaluating the peaks function.

Y — y-coordinates of points

scalar | vector | matrix

y-coordinates of points, returned as a scalar, vector, or matrix. If peaks is called with the Xm and Ym input arguments, then Y is equal to Ym. Otherwise, Y is a matrix that specifies the y-coordinates over a grid used for evaluating the peaks function.

Z — z-coordinates of points

scalar | vector | matrix

z-coordinates of points, returned as a scalar, vector, or matrix.

More About

Peaks Function

The peaks function is useful for demonstrating graphics functions, such as contour, mesh, pcolor, and surf. It is obtained by translating and scaling Gaussian distributions and is defined as

$$z=3{(1-x)}^2{e}^{-x^2-{(y+1)}^2}-10\left(\frac{x}{5}-x^3-y^5\right)e^{-x^2-y^2}-\frac{1}{3}{e}^{-{(x+1)}^2-y^2}.$$