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# Matlab 1

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• 1. POLYTECHNIC UNGKU OMAR ELECTRICAL ENGINEERING DEPARTMENTCourse : E5124 DATA COMMUNICATION (Lab work)Experiment : Matlab 1 – Get Familiarize (Matrices and Plot)The objective of this session is to learn: - How to launch the matlab software - Few simple calculations and formulation - Plot command and graphical outputIntroductionMatlab is a tool for doing numerical computations with matrices and vectors. It can also display informationgraphically. The best way to learn what Matlab can do is to work through some examples at the computer. Afterreading and familiarize with this exercise you will be able to solve construct own work.Starting MATLABLaunch MATLAB by double-clicking on the MATLAB icon on your Windows desktop. When you start MATLAB, aspecial window called the MATLAB desktop appears. The desktop is a window that contains other windows. Themajor tools within or accessible from the desktop are (refer Fig 1): - The Command Window - The Command History - The Workspace - The Current Directory - The Help Browser - The Start button 1
• 2. Fig 1 : The graphical interface to the Matlab workspaceTable below shows arithmetic operators for calculation and equation in Matlab application.As an example of a simple interactive calculation, just type the expression you want to evaluate. Lets start at thevery beginning. For example, lets suppose you want to calculate the expression, 1 + 2 x 3. You type it at the promptcommand (>>) as follows, 2
• 3. >> 1+2*3 ans = 7You will have noticed that if you do not specify an output variable, MATLAB uses a default variable ans, short foranswer, to store the results of the current calculation. Note that the variable ans is created (or overwritten, if it isalready existed). To avoid this, you may assign a value to a variable or output argument name. For example, >> x = 1+2*3 x= 7will result in x being given the value 1 + 2 x 3 = 7. This variable name can always be used to refer to the results of theprevious computations. Therefore, computing 4x will result in >> 4*x ans = 28.0000Exercise1. Matrix1.1 Insert the following expression and observe the result. >>aa=[l 3 4; 5 7 8; 2 3 5] Observation >> y=[10; 9; 8] Observation 3
• 4. 1.2 Insert both expressions. >>aa=[l 3 4; 5 7 8; 2 3 5]; >> y=[10; 9; 8]; Now obtain result for following expression >>aay Observation >>inv(aa)*y Observation >> [inv(aa)*y aay] Observation Explain your observation for expression [inv(aa)*y aay] _____________________________________________________________________________________ _____________________________________________________________________________________2. Matrix Loop2.1 Insert following expression and obtain result 4
• 5. >> a = [ 0.8 0.1; 0.2 0.9 ] Observation >> x = [ 1; 0 ] Observation2.2 Type below expression and state your observation >> a = [ 0.8 0.1; 0.2 0.9 ]; >> x = [ 1; 0 ]; >> for i = 1:20, x = a*x, end Observation 5
• 6. 3. Plot MATLAB has an excellent set of graphic tools. Plotting a given data set or the results of computation is possible with very few commands. You are highly encouraged to plot mathematical functions and results of analysis as often as possible. Trying to understand mathematical equations with graphics is an enjoyable and very e±cient way of learning mathematics. Being able to plot mathematical functions and data freely is the most important step, and this section is written to assist you to do just that.3.1 Let say, your given few samples of variable which need to find out their performance rate. Now, insert following expression:- >> a=[1 2 3 4 6 4 3 4 5] Observation >> b=a+2 Observation3.2 Use plot command to plot your result. >> plot(b) Observation >> grid on Observation 6
• 7. 3.3 Use label and title command to provide information at graph. Type this command step by step in order to observe result. Before you type command, display your Matlab window panel and graph window side by side in order to get better view. >> xlabel(Sequence of b) >> ylabel(b value) >> title(‘Graphical output for b sequence of number’) Observation3.4 Bar command used to plot bar graph which able to show us the statistical result. >> bar(b) >> xlabel(Number of sample) >> ylabel(Weight of random samples in kg) Observation 7
• 8. >> plot(b,*)>> axis([0 12 0 10]) Observation What did you see from both graphs? Explain. ______________________________________________________________________________________ ______________________________________________________________________________________3.5 To make a graph of y = sin(t) on the interval t = 0 to t = 10, do the following steps: >> t = 0:.3:10; >> y = sin(t); >> plot(t,y) >> title(Sine wave ) >> xlabel(‘Time, t) >> ylabel(Amplitude) Observation 8
• 9. 3.6 Plotting multiple wave or result in single graph. Execute following command and make your observation. Insert title and label by yourself.>> t=0:0.1:30;>> y1=sin(t);>> y2=cos(t);>> plot(t,y1,--,t,y2,-r) Observation>> t=0:0.1:30;>> y1=sin(t).*t;>> y2=cos(t).*t;>> plot(t,y1,--,t,y2,-r) Observation 9
• 10. 3.7 Subplot The subplot is used to put multiple plots on the same MATLAB figure window. subplot(pqr) - p & q represent matrixes, r locating position for plotted graph a) Write the following expression and obtain the result. >> x = 0 : 0.1 : 3 *pi; >> y = sin(x); >> z = cos(x); >> subplot(222) >> plot(x,y) >> title(Sine wave y) >> xlabel(time, x) >> ylabel(Amplitude, y) >> subplot(223) >> title(x and z) >> subplot(224) >> plot(x,y,-,x,z, -- ) >> title(x and [y z]) b) Once complete your subplot, insert label and title for each graph individually. Use example as given in above command. Observation 10
• 11. c) Discrete sample graphical output. Type following command and make observation. State the differences between both results. >> p=0:0.05:5; >> q=sin(p.^2); >> plot(p,q); Observation >> p=0:0.05:5; >> q=sin(p.^2); >> stem(p,q); ObservationReflection____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ 11