Engineering 5: engineering methodology matlab Reference Summary

control-C aborts a Matlab calculation in progress

% comments to the right of % are ignored by Matlab

; ; at end of a command suppresses printing

... ... at end of a line continues on the next line

>> quit quits Matlab without saving changes

>> exit quits Matlab without saving changes

>> clc clears command window

>> clf clears current figure

>> clear clears (destroys) all existing variables

>> casesen off turns case sensitivity off (Time = time)

>> casesen turns case sensitivity on (this is the default)

>> who lists variables that you have defined

>> whos lists variables with sizes and imaginary parts

>> size(A) lists the size of a matrix A

>> help lists help topics

>> save saves all variables in file matlab.mat

>> load recovers saved variables from file matlab.mat

>> save data1 A C saves variables A and C in file data1.mat

>> save data2.dat Z /ascii saves variable Z in ascii file format in file data2.dat

>> load data1 restores variables A and C from file data1.mat

>> load data2.dat reads data from file data2.dat and puts it in matrix data2

>> labtest executes commands in file labtest.m (previously created)

>> what shows directory listing of available m-files

>> echo displays commands in m-file as they are executed

>> type labtest displays the contents of file labtest.m without executing it

>> C = [1.5, 3.1, -4; 2.3, -5.8, 12.3; 0, 1, -3.1] creates 3 by 3 matrix C with values shown

>> C(2,1) = 9.2 replaces the 2.3 with a 9.2 in example matrix C above

>> H = 1:8 or H[1:8] generates the vector H = [1,2,3,4,5,6,7,8]

>> H1 = 1:1:8 (start_value=1, increment=1, end_value=8) generates the vector H1 = [1,2,3,4,5,6,7,8]

>> Q = 0.0: 0.5: 2.5 generates the vector Q = [0.0, 0.5, 1.0, 1.5, 2.0, 2.5]

>> v = linspace(0,pi,111) generates a vector v with 111 values between 0 and pi

>> D = C(:, 1) copies first column of matrix C into vector D

>> x = input(‘Enter values for x’) prompts user for the contents of variable x

>> format long prints numbers using 15 significant digits

>> format short prints numbers using 5 significant digits

>> format long e prints numbers in scientific notation with 15 significant digits

>> format short e prints numbers in scientific notation with 5 significant digits

>> format + prints matrices with only + and - values

>> format compact prints matrices without so much white space between elements

>> format loose opposite of above

>> disp (x) prints contents of x on screen without variable name

>> disp (‘your text here’) prints ‘your text here’ on screen

>> fprintf (‘temp is %4.1f degrees \n’, x) prints ‘temp is 29.2 degrees’ on screen if x = 29.245

>> plot (p,q) plots graph with p vector on abscissa and q vector on ordinate

>> title (‘Graph Title’) puts Graph Title on existing plot

>> xlabel (‘time in sec’) puts label ‘time in sec’ under x-axis of plot

>> ylabel (‘height in m’) puts label ‘height in m’ under y-axis of plot

>> grid draws grid background on plot

>> pause pauses execution of a Matlab program until any key is pressed

>> pause (3) pauses execution of a Matlab program for 3 seconds
special values: pi, i, j, Inf, NaN, clock, date, eps, ans

special matrices: magic (3), zeros (3,2), ones (2,4), eye (3), pascal (5)

Scalar operations: a + b, a - b, a*b, a/b, a\b, a^b

Element-by-element array operations: a + b, a - b, a.*b, a./b, a.\b, a.^b

% function returning two output variables from one input variable

% usually read in from a “.m” file, called “stat.m” in this case

n = length(x);

mean = sum(x)/n;

stdev = sqrt(sum((x-mean).^2)/n);

output(1) = mean;

output(2) = stdev;

% function returning one array “name” from two input variables

% if read in from “.m” file, would have name “dummy.m”

name(1) = cos(arg1.^2);

name(2) = arg2(1)*arg1;
Numerical integration:

[x,t] = ode23(‘dummy’, start_t, stop_t, initial) % where initial is an array of initial conditions