5 functions and files.pdf

8/11/2019 5 Functions and Files.pdf

1/35

MATLABFunctions and Files

Cheng-Liang ChenPSELABORATORY

Department of Chemical EngineeringNational TAIWAN University


2/35

Chen CL 1

Using Files filename1.m

Used for MATLAB programs and for some MATLAB functions M-files are ASCII (American Standard Code for Information Interchange)

files that are written in the MATLAB language(Can be created using any word processor or text editor)

filename2.mat

Used to save the names and values of variables created during aMATLAB session

MAT-files arebinaryfiles (more compact storage thanASCIIfiles) readable only by the software that created them

ASCII Data Files Header: comments describing what the data represents, the date it was

created, who created the data . . . One or more lines of data


3/35

Chen CL 2

Controlling Input and Output

speed = 63;disp(The predicted speed is:)

disp(speed)

The predicted speed is:

63


4/35

Chen CL 3

Input/Output Commands

Command Description

disp(A) Displays the contents, but not the name, of thearray A.

disp(text) Displays thetext stringenclosed within single quotes.

format Controls the screens output display format (Table3.3-2).

fprintf Performs formatted writes to the screen or to a file (seeAppendix C).

x=input(text) Displays thetextin quotes, waits for user input from thekeyboard, and stores thevalue in x.

x=input(text,s) Displays thetextin quotes, waits for user input from thekeyboard, and stores the input as a string in x.

k=menu(title,option1,option2,...)

Displays a menu whose title is in the string variable title,and whose choices are option1,option2,. . .


5/35

Chen CL 4

Ex: Design of A Parallel-plate CapacitorCapacitors are widely used in electric circuits. A capacitor stores energy bymaintaining the charge separation produced when a voltage is applied to thedevice. A parallel-plate capacitor is constructed from two or more parallelconducting plate, each having anarea A and separated from each other by air oranother dielectric material such as mica or paper. If the plates are separated by adistanced, the devicescapacitance C, which is a measure of its energy storagecapacity, can be computed from the formula

C= (n 1) Ad

where n is the number of platesand is the permittivity of the dielectric material.

The unit of capacitance is thecoulomb/voltand is called thefarad(F). Suppose

we use plates having an area A= 20 centimeters2, separated by a distance d= 4

millimeters with air, for which= 8.85 1012 farad/meter. Construct a table toselect the number of plates needed to obtain a desired capacitance value. Assume

that no more than 10 plates will be used.

C C


6/35

Chen CL 5

Ex: Design of A Parallel-plate Capacitor% Program capacitor.m

% Generates a table of capacitance values.

%

% Define the values of the constants.

permittivity = 8.85e-12;

A = 20/100^2; % Convert A to square meters

d = 4/1000; % Convert d to meters

%

n = [2:10]; % Vector n is # of plates% Generates capacitance values

% (Multiply by 10^12 for

% display purposes)

C = ((n-1)*permittivity*A/d)*1e12;

%

table(:,1) = n; % Create first columntable(:,2) = C; % Create second column

% Display table heading

% and table itself.

disp(No. Plates Capa.(F)xe12)

disp(table)

No. Plates Capa.(F)xe12

2.0000 4.4250

3.0000 8.8500

4.0000 13.27505.0000 17.7000

6.0000 22.1250

7.0000 26.5500

8.0000 30.9750

9.0000 35.4000

10.0000 39.8250

Ch CL 6


7/35

Chen CL 6

Numeric Display Formats

Command Description and Example

format short Four decimal digits (the default);13.6745

format long 16 digits; 17.27484029463547

format short e Five digits (four decimals) plus exponent;6.3792e+03

format long e 16digits (15decimals) plus exponent;6.379243784781294e-04format bank Two decimal digits; 126.73

format + Positive, negative, or zero; +

format rat Rational approximation;43/7

format compact Suppresses some line feeds

format loose Resets to less compact display mode

Ch CL 7


8/35

Chen CL 7

User Input

TheInput function displays text on the screen, waits for the user

to enter something from the keyboard, and then stores the inputin the specified variable

x = input(Please enter the value of x: )

Calender = input(Enter the day of the week: , s)

k = menu(title, option1, option2,...)

Demo the following in the class:

k = menu(Choose a data marker, o, *,x);type = [o, *,x];

x = [1,2,3,4]; y = [2,4,3,5];

plot(x,y, x,y, type(k),LineWidth,2,MarkerSize,3)

set(gca,LineWidth,2,FontSize,16)

title(Test the use of menu,FontSize,16)

Ch CL 8


9/35

Chen CL 8

Test Your Understanding

T3.0-1 Write a script file to compute and display a table toconvert from radians to degrees. Use five values for the radian

angle: 1, 2, 3, 4,and5radians. Be sure to label each column in the

table.

T3.0-2 The volume V of a sphere depends on its radius r asfollows: V = 4r3/3. Write a script file to compute and display

a table showing the volume in cubic meters versus the radius in

meters, for1 r 2, in increments of0.1. Label each column.

T3.0-3 The surface area A of a sphere depends on its radius r as

follows: A = 4r2. Write a script file that prompts the user to

enter a radius, computes the surface area, and displays the result.

Ch CL 9


10/35

Chen CL 9

Some Common Mathematical FunctionsExponential

exp(x) Exponential; ex

sqrt(x) Square root;xLogarithmic

log(x) Natural logarithm;ln(x)

log10(x) Common (base10) logarithm; log(x) = log10(x)

Complex

abs(x) Absolute value;xangle(x) Angle of a complex numberx

conj(x) Complex conjugate

imag(x) Imaginary part of a complex numberx

real(x) Real part of a complex number x

Numericceil(x) Round to the nearest integer towardfix(x) Round to the nearest integer toward zero

round(x) Round toward the nearest integer

sign(x) Sigmum function: +1 ifx >0; 0 ifx= 0;1 ifx


11/35

Chen CL 10

Complex Number Functions

x = - 3 + 4 i ;

y = 6 - 8 i ;mag_x = abs(x)

mag_x =

5.0000

mag_y = abs(y)

mag_y =

10.0000

mag_product = abs(x*y)50.0000

angle_x = angle(x)

angle_x =

2.2143

angle_y = angle(y)

angle_y =

-0.9273

sum_angles = angle_x + an

sum_angles =

1.2870

angle_product = angle(x*y

angle_product =

1.2870

Chen CL 11


12/35

Chen CL 11


T3.1-1For several values ofx and y, confirm that ln(xy) = ln x+ ln y.

T3.1-2

Find the magnitude, angle, real part, and imaginary part of the

number 2 + 6i.

Chen CL 12


13/35

Chen CL 12

Trigonometric Functions

Trigonometric

cos(x) Cosine; cos x

cot(x) Cotangent; cot x

csc(x) Cosecant; csc x

sec(x) Secant; sec x

sin(x) Sine; sin x

tan(x) Tangent; tan xInverse trigonometric

acos(x) Inverse cosine;cos1x

acot(x) Inverse cotangent;cot1x

acsc(x) Inverse cosecant;csc1x

asec(x) Inverse secant; sec1x

asin(x) Inverse sine;sin1x

atan(x) Inverse tangent;tan1x

atan2(y,x) Four-quadrant inverse tangent

Chen CL 13


14/35

Chen CL 13


T3.1-3For several values ofx, confirm that eix = cos x+i sin x.

T3.1-4

For several values of x in the range 0

x

2, confirm that

sin1 x+ cos1 x= /2.

T3.1-5

For several values of x in the range 0 x 2, confirm thattan(2x) = 2 tan x/(1 tan

2

x).

Chen CL 14


15/35

Chen CL 14

Hyperbolic functions

Hyperbolic

cosh(x) Hyperbolic Cosine; cosh x= (ex +ex)/2

coth(x) Hyperbolic Cotangent;cosh x/ sinh x

csch(x) Hyperbolic Cosecant;1/ sinh x

sech(x) Hyperbolic Secant;1/ cosh x

sinh(x) Hyperbolic Sine;sinh x= (e

x

ex

)/2tanh(x) Hyperbolic Tangent;sinh x/ cosh x

Chen CL 15


16/35

Chen CL 15

Inverse Hyperbolic functions

Inverse hyperbolicacosh(x) Inverse hyperbolic cosine;

cosh1 x= ln(x+

x2 1), x 1acoth(x) Inverse hyperbolic cotangent;

coth1 x= 12

ln(x+1x1

), x >1 orx

5 functions and files.pdf

Documents