MATLAB Function Reference
ezcontour

Easy to use contour plotter

Syntax

• ```ezcontour(f)
ezcontour(f,domain)
ezcontour(...,n)
```

Description

`ezcontour(f)` plots the contour lines of f(x,y), where `f` is a string that represents a mathematical function of two variables, such as x and y.

The function f is plotted over the default domain: -2 < x < 2, -2 < y < 2. MATLAB 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.

`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.

`ezcontour` automatically adds a title and axis labels.

Remarks

Array multiplication, division, and exponentiation are always implied in the expression you pass to `ezcontour`. For example, the MATLAB syntax for a contour plot of the expression,

• ```sqrt(x.^2 + y.^2)
```

is written as:

• ```ezcontour('sqrt(x^2 + y^2)')
```

That is, `x^2` is interpreted as `x.^2` in the string you pass to `ezcontour`.

Examples

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

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

• ```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 string is written on three lines and concatenated into one string using square brackets.

Pass the string variable `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)

```

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

`contour`, `ezcontourf`, `ezmesh`, `ezmeshc`, `ezplot`, `ezplot3`, `ezpolar`, `ezsurf`, `ezsurfc`