matlab lect 2.pptx

7/27/2019 Matlab lect 2.pptx

http://slidepdf.com/reader/full/matlab-lect-2pptx 1/25

Sana Zahid



Problem 1 A particular circular cylindrical tank is 15 m tall andhas a radius 8 m. We want to construct another

cylindrical tank with a volume 20 % greater but havingthe same height. How large must its radius be?



Solution r=8;

h=15;

V= pi*r^2*h; V=V+0.2*V or V=1.2*V;

r=sqrt(V/(pi*h))



Managing Working Session



Polynomial Rootsx 3 - 7x2 + 40x – 34 = 0

MATLAB commands;

>>a= [1,-7,40,-34];>>roots(a)

ans =

3.0000 + 5.000i

3.0000 - 5.000i

1.0000



Saving Data

» clear » D = 2;

» v = 3;

» rho = 1000;

» mu = 0.001;

» NRe = D*v*rho/mu;

» f = 0.076*NRe^(-0.25);

»

» save data1 D v rho mu NRe f



Loading Data

» clear » load data1

» who

Your variables are:

D f rho

NRe mu v

» D

D =

2



Common Mathematical Functions

exp (x)

sqrt (x)

log (x)

log10 (x)cos (x)

sin (x)

tan (x)

acos (x)asin (x)

atan (x)



Problem:

Determine how many elements are in the array cos(0):0.02: log10(100). Determine the 25th element.

Find the roots of the polynomial 290-11x+6x2

+ x3



Plotting With MATLAB

plot (x,y)

grid

gtext(‘ temperature ’) title(‘ graph between temp, press & vol’)

xlabel(‘ pressure ‘)

ylabel(‘ volume ‘) Plot (x,y ,’ + ‘)



Problem:

Plot the function s=2 sin(3t+2)+√(5t+1) over theinterval 0<=t<=5. put a title on the plot and properly label the axes. The variable s represents speed in feetper second; the variable t represents time in seconds



Linear Algebraic equations

6x + 12y +4z = 70

7x – 2y +3z = 5

2x +8y –

9z = 64>>A = [6,12,4;7,-2,3;2,8,-9];

>>B = [70;5;64];

>>Solution = A\B

Solution =3

5

-2



Problem:

Use the Matlab to solve the following set of equations.

6x-4y+8z= 112

-5x+7z-3y=75 14x+9y-5z=-67



Script file and Editor/Debugger

Two ways to operate with MATLAB;

1. Interactive mode (for small calculations)

2. Script File (for complex or big problems)

MATLAB programs are saved in .m format.

M-files are built with the Editor/Debugger .



M-files

1. Script files; contains a sequence of MATLABcommands, and is useful when you need to use

many commands or arrays with many elements. 2. Function files; useful when you need to repeat the

operation of a set of commands. You can create yourown function files. (Detail in Chapter 3)



How to run script file? Use of Comments?

>> % Mass Transfer Program

MATLAB ignores every thing to the right of the %symbol



Example of Script File

% Program example.m

% This program computes the sine of

% the square root and displays the results.x = sqrt ([5:2:30]);

y = sin (x);

z = cos (x);plot(x,y,x,z)



Debugging

Debugging; process of finding and removing the“bugs” or errors in a program.

Syntax Error; related to typing or grammaticalmistake, MATLAB detects it automatically.

Runtime error; are due to incorrect formula or

input. We have to find and fix it. e.g. Division by Zero.



Programming Style

1. Comment Section2. Input Section

3. Calculations Section4. Output Section

See Example of a good script file in your book at

Page 37



For Changing MATLAB Look



Input/Output commands

disp (A)

disp ( ‘ Text ’ )

x = input ( ‘ text ’ )



num2str command

% This m-file calculates the area of a circle,

% and displays the result.

radius = 2.5;

area = pi * 2.5 ^ 2;

disp (area)



Assignment

Problems:

Section 1.1( 1 to 6 group 1)

Section 1.1 (6 to 12 group 2)





Practice more and more

&Have a nice dash.

(b +ve)

matlab lect 2.pptx

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