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Matlab for Civil Engineers

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Matlab for Civil Engineers Engr. Faisal ur Rehman Matlab Tutorial Engr. Faisal ur Rehman http://enggprog.com (Engineering Programs) Introduction Matlab Basic Commands Matlab is software for Engineeirng Calculation. The main window is command window with command prompt '>>' The basic and important Matlab command is listed below: Assigning value to a Variable: >>x=5 >>y = x+4 To Define a Row Matrix of size 1x6: >>A = [1 2 3 4 5 6] Defining a Row Matrix without display of answer variable ( use semicolon at the end of command): >>B = [1 3 3 7 5 6]; To Define a Column Matrix of size 6x1: >>C = [1;2;3;4;5;6] To Define a Square Matrix of size 6x6: >>D = [1 2 3 2 7 3;2 8 7 4 3 4;0 1 9 8 6 4;9 6 5 4 3 3;3 4 5 1 2 7;9 8 7 0 5 1] Finding Transpose of Matrix: >>D' Finding the Determinant of Matrix: >>det(D) enggprog.com (Engineering Programs) 1 Matlab for Civil Engineers Engr. Faisal ur Rehman Finding Inverse of Matrix: >>inv(D) Another command of Matrix Inverse is: >>D^-1 Note: Caret (^) symbol is used for taking power. To find the Matrix Multiplication and store result in Matrix E (6x1): >>E=D*C To find the inverse of square matrix D and multiply with Matrix C: >>F=D^-1*C Another way of above calculation is: >>G=inv(D)*C Third method of above calculation is: >>H=D\C To define a Null Matrix 5x4 size: >>I = zeros(5,4) To define a Square Null Matrix of 6x6 size: >>J=zeros(6) To define the Identity Matrix of size 6x6: >>K=eye(6) To define a Row Martrix with elements from 1 to 10 with step size of 0.05: >>L = [1:0.05:10] To clear the display of command window: >>clc To save only variable C,F and G to Workspace file named myvar1.mat: >> save('myvar1.mat','C','F','G') To save all variables to workspace named myvar2.mat: >>save myvar2.mat To remove variable A, B, and D from Workspace: >>clear('A', 'B','D') enggprog.com (Engineering Programs) 2 Matlab for Civil Engineers Engr. Faisal ur Rehman To clear all variables from Matlab Workspace: >>clear all To load only variable H and I from myvar2.mat file: >>load('myvar2.mat','H','I') To load all variable from myvar2.mat file: >>load myvar2.mat To find the sine of given matrix: >>M = 2*sin(L); Note: Angle Input is taken as radian. To perform scalar multiplication of matrix A and B: >>N = A.*B Note: dot (.) symbol is used for element wize operation. To plot to arrays: >>plot(L,M) To plot with dot marker: >>plot(L,M,'.') To plot with asterisk (*) marker and line of red color: >>plot(L,M,'*-r') To perform complex number calculation on a and b: >> a = 2 +5i; >>b = 9 + 6j; >>a+b >>a-b >>a*b >>a/b To open M file Editor: Desktop>Editor Save a new file by the name cmr.m and write the following: % Crammer Rule Calc A=input('Enter a Square Matrix of Size mxm'); B=input('Enter a Column Matrix of Size mx1'); X=A\B; disp('X (mx1) is :') disp(X) To execute above m file, write: cmr in command window. enggprog.com (Engineering Programs) 3 Matlab for Civil Engineers Engr. Faisal ur Rehman Following is the code of qdr.m file for Quadratic Equation: %quadratic root calc using quadratic formula: a=input('Enter the coefficient of quadratic equation - a = '); b=input('Enter the coefficient of quadratic equation - b = '); c=input('Enter the coefficient of quadratic equation - c = '); x1=(-b+sqrt(b^2-4*a*c))/(2*a) x2=(-b-sqrt(b^2-4*a*c))/(2*a) To find help of given command: >>help det enggprog.com (Engineering Programs) 4