ezcontour

(Not recommended) Contour plotter

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ezcontour is not recommended. Use fcontour instead.

Syntax

ezcontour(f)
ezcontour(f,domain)
ezcontour(___,n)

Description

ezcontour(f) plots the contour lines of f(x,y), where f is a symbolic expression that represents a mathematical function of two variables, such as x and y. ezcontour automatically adds a title and axis labels.

The function f is plotted over the default domain –2π < x < 2π, –2π < y < 2π. MATLAB® software chooses the computational grid according to the amount of variation that occurs; if the function f is not defined (singular) for points on the grid, then these points are not plotted.

example

ezcontour(f,domain) plots f(x,y) over the specified domain. domain can be either a 4-by-1 vector [xmin, xmax, ymin, ymax] or a 2-by-1 vector [min, max] (where, min < x < max, min < y < max). If f is a function of the variables u and v (rather than x and y), then the domain endpoints umin, umax, vmin, and vmax are sorted alphabetically. Thus, ezcontour(u^2 - v^3,[0,1],[3,6]) plots the contour lines for u2 - v3 over 0 < u < 1, 3 < v < 6.

ezcontour(___,n) plots f over the default domain using an n-by-n grid. The default value for n is 60.

Examples

Plot Contour Lines of Symbolic Expression

The following mathematical expression defines a function of two variables, x and y.

f(x,y)=3(1−x)2e−x2−(y+1)2−10(x5−x3−y5)e−x2−y2−13e−(x+1)2−y2.

ezcontour requires a sym argument that expresses this function using MATLAB syntax to represent exponents, natural logs, etc. This function is represented by the symbolic expression

syms x y
f = 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);

For convenience, this expression is written on three lines.

Pass the sym f to ezcontour along with a domain ranging from -3 to 3 and specify a computational grid of 49-by-49.

ezcontour(f,[-3,3],49)

Figure contains an axes object. The axes object with title 3 exp (- ( y + 1 ) Squared baseline - x Squared baseline ) ( x - 1 ) Squared baseline -...+ exp (- x Squared baseline - y Squared baseline ) ( 10 x Cubed baseline - 2 x + 10 y toThePowerOf 5 baseline ), xlabel x, ylabel y contains an object of type contour.

In this particular case, the title is too long to fit at the top of the graph so MATLAB abbreviates the title.

Input Arguments

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Input, specified as a symbolic function or expression.

Domain to plot over, specified as a symbolic vector. domain is a 4-by-1 vector [xmin, xmax, ymin, ymax] or a 2-by-1 vector [min, max] (where, min < x < max, min < y < max). If f is a function of the variables u and v (rather than x and y), then the domain endpoints umin, umax, vmin, and vmax are sorted alphabetically

Grid points, specified as a number or a symbolic number.

Version History

Introduced before R2006a

See Also

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