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MATLAB Basics I

Variables and Assignments Vectors and Matrices. Solving Equations Functions. MATLAB Basics I. Yun Suk Jang Department of physics Kangwon National University. You use the equal sign to assign values to a variable. >> x = 7 x = 7 X the value 7 from now on.

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MATLAB Basics I

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  1. Variables and Assignments Vectors and Matrices Solving Equations Functions MATLAB Basics I Yun Suk Jang Department of physics Kangwon National University

  2. You use the equal sign to assign values to a variable. >> x = 7 x = 7 X the value 7 from now on. If y has been defined as a symbolic variable, then >> x^2 - 2*x*y + y ans = 49 – 13*y To clear the value of the variable x, type clearx. You can make very general assignments for symbolic variables and then manipulate them. >> clear x; syms x y >> z = x^2 – 2*x*y + y z = x^2 – 2*x*y + y >> 5*y*z ans = 5*y*(x^2 – 2*x*y + y) Variables and Assignments

  3. You can solve equations involving variables with solve or fzero. >> solve(‘x^2 – 2*x – 4) ans = [ 5^(1/2) + 1] [ 1 – 5^(1/2)] You can specify more than one equation as well. >>[x, y]= solve(‘x^2–y = 2’,’y–2*x = 5’) x = [ 1 + 2*2^(1/2)] [ 1 – 2*2^(1/2)] y = [ 7 + 4*2^(1/2)] [ 7 – 4*2^(1/2)] Solving Equations

  4. Vector A vector is an ordered list of numbers. You can enter a vector of any length in MATLAB by typing a list of numbers, separated by commas or space, inside square brackets. Ex) >> z = [ 2, 4, 6, 8 ] z = 2 4 6 8 >> x = 1 : 9 x = 1 2 3 4 5 6 7 8 9 >> x = 0 : 2 : 10 x = 0 2 4 6 8 10 Matrices A matrix is a rectangular array of numbers. Row and column vectors, which we discussed above, are examples of matrices. Ex) >>A=[1,2,3,4;5,6,7,8;9,10,11,12] A = 1 2 3 4 5 6 7 8 9 10 11 12 Vectors and Matrices

  5. Built-in Functions MATLAB also has several built-in constants, including pi, I (the complex number) and inf(∞). Ex) >> log(exp(3)) ans = 3 >> sin(2*pi/3) ans = 0.8660 To get an exact answer, you need to use a symbolic argument: >> sin (sym (‘2*pi/3’) ) ans = 1/2*3^(1/2) User-Defined Functions In this section we will show how to use Inline to define your own functions. Ex) >> f = inline(‘x^2 + x + 1’, ‘x’) f = Inline function: f(x) = x^2 + x + 1 We conclude this section by remarking that one can also define functions of two or more variables: Ex) >> g = inline(‘u^2 + v^2’,‘u’,‘v’) g = inline function: g(u, v) = u^2 + v^2 Functions

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