1. ENEE222 Elements of
Discrete Signal Analysis
Lab 11 1

2. Prepare your working environment
Download the script for lab 11 from ELMS or:
terpconnect.umd.edu/~rssaketh/ene222/lab
Move files to your desktop
Double click the MATLAB icon on the desktop
In MATLAB, set “Current Folder” to your desktop
Double click the file “lab_11_script.zip” inside MATLAB 2

3. Items 1&2: Anonymous Functions
Single-line command
Created on the fly
Can be used for the remainder of the session, but cannot be saved as a function M-file
Rather recent, and powerful feature of Matlab.
Example:
fun1 (x,y) cos(1/x+y)
Function Name
Function Name
Operator Used to Construct a Function Handle
List of Input Arguments
Body of the Function 3

4. Items 3&4: Function Handles
The function handle has the following two properties:
Directly invokable:
fun1(-0.5)
Can be an input argument to anther function:
max2(fun1)
A function handle of a built-in / user-defined function can be obtained with the help of operator, e.g.,
myCosine 4

5. Item 5: Meshgrid
We have seen how z = f(x,y)=x+2y can be evaluated over a rectangular grid (e.g., with axes x=1:10 and y=1:10 ) using FOR loops.
This can also be done without FOR loops using MESHGRID, which generates two matrices with the x- and y-coordinates of the grid points. For example,
x=[-1:1:3]; y=[0:0.2:1];
[X,Y]=meshgrid(x,y);
X varies horizontally only, and Y varies vertically only.
X and Y can be used as arguments in any array-friendly function. (cos, exp, .* ) 5

6. Item 5: Linspace We are familiar with the following syntax:
t = lbound : stepsize : ubound
For example, to generate 11 elements between 0 and 1, we can use:
t=0:0.1:1
Alternatively, we may use LINSPACE:
t = linspace(lbound,ubound,#points)
The same result as above is obtained by
t = linspace(0,1,11) 6

7. Item 6: Contour
A contour plot consists of a number of lines on the x-y plane over which a function z = f(x,y) takes constant value; it thus depicts the variation of a function in discrete terms.
contour(Z) % axes labeled by indices
contour(X,Y,Z) % actual coordinates
“Matrix” axis mode (axis ij) is default for imshow
“Cartesian” axis mode (axis xy) is default for contour 7

8. Item 7: 3-D Plotting MESH: 3-D wire-frame surface
SHADING FLAT: remove mesh lines
SURF: 3-D surface, basically a filled mesh
SURFC: adds a 2-D contour plot on the x-y plane
VIEW(AZIMUTH, ELEVATION)
The two arguments represent (respectively) horizontal and vertical rotations of an observer facing the origin from an initial position in the far negative y-direction.
Both are quoted in degrees. 8