MATLAB Function Reference

fplot - Plot function between specified limits

Syntax

fplot(fun,limits) fplot(fun,limits,LineSpec) fplot(fun,limits,tol) fplot(fun,limits,tol,LineSpec) fplot(fun,limits,n) fplot(fun,lims,...) fplot(axes_handle,...) [X,Y] = fplot(fun,limits,...)

Description

fplot plots a function between specified limits. The function must be of the form y = f(x), where x is a vector whose range specifies the limits, and y is a vector the same size as x and contains the function's value at the points in x (see the first example). If the function returns more than one value for a given x, then y is a matrix whose columns contain each component of f(x) (see the second example).

fplot(fun,limits) plots fun between the limits specified by limits. limits is a vector specifying the x-axis limits ([xmin xmax]), or the x- and y-axes limits, ([xmin xmax ymin ymax]).

fun must be

The name of an M-file function
A string with variable x that may be passed to eval, such as 'sin(x)', 'diric(x,10)', or '[sin(x),cos(x)]'
A function handle for an M-file function or an anonymous function (see Function Handles and Anonymous Functions for more information)

The function f(x) must return a row vector for each element of vector x. For example, if f(x) returns [f1(x),f2(x),f3(x)] then for input [x1;x2] the function should return the matrix

f1(x1) f2(x1) f3(x1)
f1(x2) f2(x2) f3(x2)

fplot(fun,limits,LineSpec) plots fun using the line specification LineSpec.

fplot(fun,limits,tol) plots fun using the relative error tolerance tol (the default is 2e-3, i.e., 0.2 percent accuracy).

fplot(fun,limits,tol,LineSpec) plots fun using the relative error tolerance tol and a line specification that determines line type, marker symbol, and color. See LineSpec for more information.

fplot(fun,limits,n) with n >= 1 plots the function with a minimum of n+1 points. The default n is 1. The maximum step size is restricted to be (1/n)*(xmax-xmin).

fplot(fun,lims,...) accepts combinations of the optional arguments tol, n, and LineSpec, in any order.

fplot(axes_handle,...) plots into the axes with handle axes_handle instead of the current axes (gca).

[X,Y] = fplot(fun,limits,...) returns the abscissas and ordinates for fun in X and Y. No plot is drawn on the screen; however, you can plot the function using plot(X,Y).

Remarks

fplot uses adaptive step control to produce a representative graph, concentrating its evaluation in regions where the function's rate of change is the greatest.

Examples

Plot the hyperbolic tangent function from -2 to 2:

fnch = @tanh;
fplot(fnch,[-2 2])

Create an M-file, myfun, that returns a two-column matrix:

function Y = myfun(x)
Y(:,1) = 200*sin(x(:))./x(:);
Y(:,2) = x(:).^2;

Create a function handle pointing to myfun:

fh = @myfun;

Plot the function with the statement

fplot(fh,[-20 20])

Additional Example

This example passes function handles to fplot, one created from a MATLAB^® function and the other created from an anonymous function.

hmp = @humps;
subplot(2,1,1);fplot(hmp,[0 1])
sn = @(x) sin(1./x);
subplot(2,1,2);fplot(sn,[.01 .1])