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CS 170 – Intro to Scientific and engineering Programming

CS 170 – Intro to Scientific and engineering Programming. Functions. What is a function? In Math In CS Hundreds of Matlab Functions! Input = Argument Can we have more than one argument? Can we have an array as a function argument? Which functions have we used so far?

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CS 170 – Intro to Scientific and engineering Programming

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  1. CS 170 – Intro to Scientific and engineering Programming

  2. Functions • What is a function? • In Math • In CS • Hundreds of Matlab Functions! • Input = Argument • Can we have more than one argument? • Can we have an array as a function argument? • Which functions have we used so far? • Find their arguments • Is ‘end’ a function?

  3. Matrix building functions • zeros(n,m) Zeros • ones(n,m) Ones • eye(n,m) Zeros except that diagonal elements equal 1 • rand(n,m) Random numbers uniformly distributed in the range from 0 to 1 • randn(n,m) Random numbers normally distributed with mean equal to 0 and variance equal to 1

  4. Polymorphism • Ex. sqrt • Scalar • Array • What does this mean? • Function call with multiple forms • Is it useful? • Another form: varying number of arguments • Ex. sum

  5. Returning more than one objects • Array of objects • Ex. max

  6. Keyboard input • What is a user interface? • Why do we need user input? • Where is the user input entered? • fave = input('Please type your favorite vector: '); • What will be the value of fave?

  7. Formatted output • What is an output? • Why should we format our output? • Conversion and Escape characters • Ex. >> fprintf('No.: %d, cost= %5.2f.\nTotal is %7.3f\n', 4, 3.1, 4*3.1); No.: 4, cost= 3.10. Total is 12.400

  8. Intro to plotting with Matlab If X is a 1-by-N (or N-by-1) vector, and Y is a 1-by-N (or N-by-1) vector, then >> plot(X,Y) creates a figure window, and plots the data in the axis. The points plotted are (X(1),Y(1)), (X(2),Y(2)), … , (X(N),Y(N)). By default, Matlab will draw straight lines between the data points, and the points will not be explicitly marked. For more info, do >> help plot Example: >> X = linspace(0,3*pi,1000); >> Y = sin(X); >> plot(X,Y)

  9. Plotting several lines If X1 and Y1 are both 1-by-N, and X2 and Y2 are both 1-by-M, then >> plot(X1,Y1,X2,Y2) will plot both sets of data on the same axis. Example >> X1 = linspace(0,pi,1000); >> Y1 = cos(4*X1).*sin(X1); >> X2 = [0 1 4 5]; >> plot(X1,Y1,X2,sqrt(X2))

  10. Questions??

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