ECE 106: Digital Computer Lab

Lab Activity Number 9

Objectives1. Create a user-defined function to be run as a stand-alone program from the command window;2. Create a user-defined function that is run from within a user-written m-file

INTRODUCTIONA function is a code segment which accepts certain inputs. These inputs are called its arguments. The function written in m-file manipulates the inputs in the manner in which code is written and provides the required results. Matlab provides us with the facility that we can also write functions ourselves to perform specific operation according to our requirement. We have to make two functions:

(i) One will accept three co-ordinates in xy-plane and plot a triangle among them. Further, each side of the triangle should have different color.

(ii) The other function accepts four co-ordinates in the xy-plane. The first three co-ordinates in this program are used to plot a triangle and the fourth co-ordinate in the (x,y) form is used to shift the triangle. The x-co-ordinate is used to shift the triangle in x direction and the y-co-ordinate is used to shift the triangle in y direction.We have to make a my_script.m file in which both of the above functions are called to plot and shift the triangle.

PROGRAMMINGplotTriangle FunctionMatlab Code: function plotTriangle(a,b,c)precision=500;abx=linspace(a(1),b(1),precision);aby=linspace(a(2),b(2),precision);bcx=linspace(b(1),c(1),precision);bcy=linspace(b(2),c(2),precision);cax=linspace(c(1),a(1),precision);cay=linspace(c(2),a(2),precision); hold onplot(abx,aby,'-b','linewidth',3)plot(bcx,bcy,'k-','linewidth',3)plot(cax,cay,'r-','linewidth',3)axis([0 10 0 10])grid ontitle('My Triangle')xlabel('X Values (units)')ylabel('Y Values (units)')

shiftTriangle FunctionMatlab Code: function [a,b,c]=shiftTriangle(a,b,c,shift)precision=500;a=a+shift;b=b+shift;c=c+shift;abx=linspace(a(1),b(1),precision);aby=linspace(a(2),b(2),precision);bcx=linspace(b(1),c(1),precision);bcy=linspace(b(2),c(2),precision);cax=linspace(c(1),a(1),precision);cay=linspace(c(2),a(2),precision); hold onplot(abx,aby,'-b','linewidth',3)plot(bcx,bcy,'k-','linewidth',3)plot(cax,cay,'r-','linewidth',3)axis([0 10 0 10])grid ontitle('My Triangle')xlabel('X Values (units)')ylabel('Y Values (units)')my_script.m FileMatlab Code:clc;clear all;close all;

x=[1 2];y=[1 6];z=[6 2]; shift=[2 4]; plotTriangle(x,y,z)[xx,yy,zz]=shiftTriangle(x,y,z,shift);Results

1-Result of plotTriangle([1 2],[1 6],[6 2])

Result of [p,q,r]=shiftTriangle([1 2],[1 6],[6 2],[2 4])

Result of running the my_script.m file

Conclusion

In this Lab I have learnt the use of Function in programming. Once a function is programmed, it can be used anywhere in our program. The greatest advantage of function is that, if a similar task is to be performed again and again, we don/t have to write the program every time. We can call the function

Also, it can be observed that function variables are not Global. They just work within the function and not stored in MATLAB Work Space.

Additionally, I have learnt the use of linspace command of MATLAB. It converts the points into vectors with desired data points in between. Also the hold on command is used to draw multiple plots on same figure.