# 2D Plotting

## Plotting y=f(x) on the interval [-.1,.1]:

First create a vector of (e.g.) 200 equally spaces values between -.1 and .1.
x1=linspace(-.1,.1,200);
Suppose f(x) is an algebraic expression of standard functions such as f(x)= x^2*sin(1/x).
Then the following computes the y values from the x values.
y1 = x1 .^ 2 .* sin(1 ./ x1);
Now put up the plot:
plot(x1,y1)
Styles and colors mady be indicated e.g. by
plot(x,y,'r--')
where r indicates red, -- indicates dashed, : indicates dotted, and * means starred.
Titles, xlabels, ylabels, and text can be added by
title('Graph Illustrating ...') ; xlabel(' ... ') ; text(x0,y0,'string') etc.
Axes can be drawn by
axis([xmin xmax ymin ymax])

can be accomplished by:
x2=linspace(-.1,.1,50);
(Note that this function oscillates less, so we take a coarser grid with only 50 points.
y2 = x2 .^2
y3 = -x2 .^2
plot(x1,y1,x2,y2,x2,y3)

## Another Way to Combine Pictures:

is to use the commands
Hold on
to cause additional pictures to be superimposed on the existing one
Hold off
to restore the default of replacing an old picture by a new one.
More sophisticated control of pictures is also possible via Matlab's handle graphics facility.

## Plotting a Function Defined in an m-file:

Contents of m-file fcnname.m on the interval [a,b] is plotted by
fplot('fcnname',[a,b])
Last Update: September 25, 2000