Excel Definitions

Ma`ruza 9

Matlabda ma`lumotlar bilan ishlash

Overview

• In this lecture, we’ll look at some commands that are useful for working with data!
• fzero
• sum, min, max, length, mean, median, std, and sort
• polyval, polyfit, polyder, polyint

fzero

• One of MATLAB’s built-in functions is “fzero”.
• fzero uses the Bisection Method to find a zero of a function f(x).
• Syntax: fzero(‘f’,x0) where f is a function defined in MATLAB and x0 is either a starting value or an interval of the form [x1 x2].
• In the second case, f(x1) and f(x2) must differ in sign.

fzero

• Example 1: Try each of the following commands:
• fzero('cos',1.5)
• z1 = fzero('cos(x.^2)', [0 sqrt(pi)])
• For Octave, to use this command, create a function M-file for cos(x.^2), such as “Sample2.m”.

fzero

• Example 2: Plot the function y=Sample1(x) on the interval [-2,2].
• Use the graph to pick a starting value x0 for fzero to locate the positive zero.
• Then try z2 = fzero('Sample1',x0).
• In MATLAB, the following should produce the same result:
• z3 = fzero('x+x.^2-x.^4',x0).

fzero

• Example 3: Create an M-file called Example3.m with this script:
• x = -2:0.01:2;
• plot(x, Sample1(x));
• z = fzero('Sample1', [1 2]);
• title('The positive zero of y = x+x^2-x^4');
• grid on;
• set(gca, 'Xtick', [-2:1 z 2]);
• %This last command specifies tick-marks on the x-axis.
• %Note that tick marks must be specified in ascending or descending order.

Working with Data

• MATLAB has several functions that can be used to work with sets of data, including:
• sum, min, max, length, mean, median, std, and sort
• Use the Help file to learn more about each!

Working with Data

• Example 4: Let x = [5 2 1 6 3]. Enter vector x and find each of the following:
• sum(x)
• min(x)
• [mx, indx] = min(x)
• max(x)
• [Mx, indx] = max(x)
• length(x)
• mean(x)
• sum(x)/length(x)
• std(x)
• sort(x)