CS 100 M Lecture 12

CS 100 M Lecture 12 - 12. Still More on Arrays Functions...

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Unformatted text preview: 12. Still More on Arrays Functions with array parameters. Row and column vectors Built-Ins: length, zeros, std Revisit: rand, randn, max Row and Column Vectors >> v = [1 2 3] v = 1 2 3 >> v = [1 ; 2 ; 3] v = 1 2 3 Observe semicolons zeros( , ) >> x = zeros(3,1) x = >> x = zeros(1,3) x = 0 0 rand( , ) >> x = rand(3,1) x = 0.2618 0.7085 0.7839 >> x = rand(1,3) x = 0.9862 0.4733 0.9028 randn( , ) • >> x = randn(1,3) • x = • 0.2877 -1.1465 1.1909 • >> x = randn(3,1) • x = • 1.1892 •-0.0376 • 0.3273 Normal Distribution with Zero Mean and Unit STD-3-2-1 1 2 3 10000 20000 30000 40000 50000 60000 70000 80000 90000 100000 110000 Distribution of randn(1000000,1) Affirmations >> n = 1000000; >> x = randn(n,1); >> ave = sum(x)/n ave =-0.0017 >> standDev = std(x) standDev = 0.9989 length >> v = randn(1,5); >> n = length(v) n = 5 >> u = rand(5,1); >> n = length(u) n = 5 The length function doesn’t care about row or column orientation. Augmenting Row Vectors >> x = [10 20] x = 10 20 >> x = [x 30] x = 10 20 30 >> Augmenting Column Vectors >> x = [10;20] x = 10 20 >> x = [x ; 30] x = 10 20 30 Observe semicolons! “Concatenating” Row Vectors >> x = [10 20] x = 10 20 >> y = [30 40 50] y = 30 40 50 >> z = [x y] z = 10 20 30 40 50 “Concatenating” Column Vectors >> x = [10 ; 20]; >> y = [30 ; 40 ; 50]; >> z = [ x ; y ] z = 10 20 30 40 50 Observe semicolons! Application x = linspace(0,2*pi,100); y = sin(x); x = [x x+2*pi]; y = [y y]; plot(x,y) Plot sine across [0,4*pi] and use the fact that it has period 2pi. 2...
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This note was uploaded on 02/23/2008 for the course CS 100 taught by Professor Fan/vanloan during the Spring '07 term at Cornell.

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CS 100 M Lecture 12 - 12. Still More on Arrays Functions...

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