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# 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 a 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

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).

## Examples

Plot the hyperbolic tangent function from -2 to 2:

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

For this example, you must create a file named myfun.m 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])`

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])```

expand all

### Tips

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.