matlab basics 3 vectors or arrays - university of...

MATLAB Basics 3 vectors or arrays

Anthony Rossiter

University of Sheffield

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Slides by Anthony Rossiter

For a neat organisation of all videos and resources

http://controleducation.group.shef.ac.uk/indexwebbook.html

Introduction

1. The previous video demonstrates how to use basic MATLAB functionality.

2. For more advanced problem solving there is often a requirement to repeat the same computation on a number of different variables.

3. For example, how would you form a plot of y=f(x) for -1<x<4? You would calculate f(x) at a number of different values for x.

4. MATLAB supports a vector/array notation to make handling these computations much easier.


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Defining an ROW array

MATLAB uses square brackets and commas to store a set of numbers in a single variable.


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v is a 1 by 6 array because it stores 6

values in a row vector form.

Defining a COLUMN array

MATLAB uses square brackets and semi-colons to store a set of numbers in a column form.


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v is a 6 by 1 array because it stores 6 values in a column

vector form.

Form a sketch of a simple function

MATLAB function commands such as sin, cos, log etc support data entry in array form to make computations much more efficient.


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Form a sketch of a simple function

MATLAB function plot will give a plot of 2 arrays assuming both arrays are the same length.


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Plots elements [v(1),y(1)], [v(2),y(2)],…,[v(6),y(6)]

Longer arrays


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• In practice, we may want 50-100 values to form a plot and this is tedious to enter by hand.

• MATLAB provides a convenient mechanism to automate the generation of suitable argument (or domain) values. Lower x

value

Upper x value

Number of values

Sketch with lots of values


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Illustration with limits -1 and 8 and 1000 values in total.

Note how quick and easy this is to write.

Lower x value

Upper x value

1000 values

Accessing vector array values

MATLAB uses a common sense notation to access values. The value in the ith position is accessed with the notation x(i).


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5 values

Value in 2nd position accessed by x(2)

Value in 5th position accessed by x(5)

Accessing vector array values 2

MATLAB has a short cut to find the last value in an array which is useful when you do not know the number of terms in the array.


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Value in last position accessed by x(end)

Value in last position accessed

by y(end)

Switching off display to command window

Where a vector has a large number of terms, better not to display to screen as this will flood the screen.

Here f=0:100

To switch off display, use a semi-colon at the end of the command.


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NO DISPLAY!

LIVE DEMONSTRATIONS WITH MATLAB


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Open the following and try the instructions

matlab_basics3.m

Conclusions

Demonstrated the vector/array notation in MATLAB.

1. Allows efficiency of computation and data storage.

2. The same ‘function’ can be executed on many different values using a single operation.

3. Required for the plotting function.

4. Easy to extract specific values as required.

Users recommended to finish commands with a semi-colon to prevent flooding the command window with the data output.


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Anthony Rossiter Department of Automatic Control and

Systems Engineering University of Sheffield www.shef.ac.uk/acse

For a neat organisation of all videos and resources

http://controleducation.group.shef.ac.uk/indexwebbook.html

http://creativecommons.org/licenses/by/2.0/uk/

matlab basics 3 vectors or arrays - university of...

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