Matlab-kurs
Praktiske opplysninger
Om Matlab
Matlab brukes til numeriske beregninger og visualisering av
data.
Anvendelsesområder:
- Plotting av data (Matlab)
- Matematiske funksjoner (Matlab)
- Likningsløsning (Matlab)
- Lineær algebra (matriseregning) (Matlab)
- Reguleringsteknikk (Control System Toolbox)
- Simulering (Matlab, Control System Toolbox, Simulink)
- Signalbehandling (Signal Processing Toolbox)
- Statistikk (Statistical Toolbox)
- Optimalisering (Optimization Toolbox)
- + + (20-30 toolboxer)
Arbeidsomgivelsene i Matlab
[Kap. 3]
Vi gjør oss kjent med arbeidsomgivelsene:
- Kommandovinduet med kommandolinja
- Arbeidsrommet
- Arbeidskatalogvinduet
- Kommandohistorievinduet
- Oppstartingsvinduet
- Hjelp!
We try the following simple commands from the command line (the commands
are executed by pressing Enter):
a=1+1 The response is shown in the command window.
a=2+2; The response is not shown in the command window.
a Shows the value of the variable a.
1+2 The result is assigned to the inbuilt variable ans.
ans+4 The result is 7.
d=1+2+...[Enter]
3+4 Three dots means that the command line continues.
e=1+1,f=2+2 One or more expressions - separated by semicolon or
comma - can be written on one line.
f, F Octave separates between ordinary and capital letters. f
exists, while F does not exist.
0.1, 1e-1, 2^3, exp(1), pi Various ways to enter numbers. Obs:
Desimalpunktum, ikke -komma!
Matlab functions are vectorized, i.e. functions can be called with
vectorial arguments.
t=[0:0.1:100]; Vector
f=2; %Hz Note the percent sign. It means comments.
y=sin(2*pi*f*t) y becomes a vector, too, of same length as t.
Hjelp!
Tre alternativer:
- Kommandolinje-hjelp: Eksempel: help sin (på kommandlinja)
- Hjelp-menyen
- Hjelp på Web: http://mathworks.com
Scripts
A Matlab script is a text file of name *.m containing Matlab
expressions. You can edit the script using any text editor, e.g. Notepad, or
using the inbuilt Matlab editor which can be launched via File / New.
You run the script in two ways (causing all the expressions to be execued
automatically as if they were written on the command line individually):
- By typing the script name (without the file extension m) on the
command line
- By pressing the Run-button in the toolbar in the editor
You should use scripts even for small tasks.
Example:
Enter the following expressions in an empty document in the Matlab editor:
clear;
a=1;
b=2;
c=a+b
Save the script as (e.g.) c:\temp\myscript1.m.
Run the script via the Run button
Matrix (or array) operations
Creating matrices. Getting matrix information:
A=[1,2;3,4] Cretaes matrix (or array) A.
r=[0:0.2:10] Row vector (or array)
c=[0:0.2:10]' Column vector (or array)
r(1) Returns the first element of r. Note that 1 (not 0) is the
first index.
r(end) Returns the last element of r.
x=[1,2,3]'; y=[4,5,6]'; B=[x,y] Creates matrix B from given column
vectors.
size(x) Size of x.
B(:,2) Returns column no. 2 in B.
A few special matrices:
C=eye(3) Identity matrix
D=ones(3,2) Matrix of ones
E=diag([1,2,3]) Diagonal matrix
Matrix calculations:
Matrices can be used in matrix calculations. A few examples:
F=C+E
A*inv(A)
Elementwise calculations:
x=[1,2,3]'; y=[4,5,6]'; z=x.*y Note the operator .*
Plotting
Vi prøver
plott1.m,
som demonstrerer plotting.
Vi prøver figureditering via menyvalg og funksjonsknapper i figurvinduet.
Vi prøver
plott_edit.m, som illustrerer figureditering via kommandoer.
[Fagets hjemmeside] [Fagets framdriftsplan]
Oppdatert 24.11.05 av Finn
Haugen, faglærer (e-postadresse: finn@techteach.no).
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