Lec5 MatlabProgramming

# Lec5 MatlabProgramming - Opinion Polls Physics 257 Lecture...

This preview shows pages 1–3. Sign up to view the full content.

Physics 257 Lecture 5: More fun with Matlab Prof. Matt Dobbs Physics Department, McGill U. Prof. M. Dobbs, Physics 257 October 17. 2007 3 Opinion Polls ± Question from a student- how do we interpret: z The poll surveyed 1,002 Quebecers from Oct. 10 to Oct. 22. It is considered accurate to within 4.3 percentage points, 19 times out of 20. ± Let’s re-write one of our physics results in the same language: z We measure the period of a pendulum T= 5.1 ± 0.1 seconds z The errors are random and we think the central limit theorem applies, such that they are distributed Gaussian. ± This physics result predicts a period of ____ seconds. It is considered accurate within ____ seconds, _____ times out of 100. Matlab programming Prof. M. Dobbs, Physics 257 October 17. 2007 5 How a computer stores numbers ± The only numbers a computer can store are 1 and 0. z 1 bit boolean number: 0/1 = False/True ± But it can build integers out of binary numbers: z Base 2 (binary), 8 (octal), 10(decimal), 16(hexidecimal) z With 16 bits it can count from 0 to 2 16 -1 = 65535. ¾ 16 bit unsigned integer 0 Æ 65535 z Using 1 bit as the sign (+ or -), it can represent negative numbers too. ¾ 16 bit signed integer -32767 Æ 32768 ¾ 32 bit signed integer (“long”) -2 147 483 647 Æ 2 147 483 648 ± It can build regular text as well by using 8 bits per character (a “byte”), representing 256 unique symbols. We assigned each letter (or other key) in the alphabet to one of these numbers. z The most common coding of this style is called ASCII. ± Floating point numbers can also be built out of binary: z digital devices can’t store them. Built up from integers. z analog devices can store them, with noise.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Prof. M. Dobbs, Physics 257 October 17. 2007 6 Goals for Scientific Programming ± The program should solve the problem z Correctly (the answer should be correct!) z Efficiently (without wasting time/space) ¾ The top two are obvious! z Readably / user-friendly (other people should be able to read it) ¾ With modern computers, we almost always choose to trade speed for readability. z Modularly – so that it is easy to understand. ¾ For this we use functions or subroutines. Prof. M. Dobbs, Physics 257 October 17. 2007 7 Script Files ± Matlab program files have .m extensions. ± We can put any number of commands in a .m file. z
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 5

Lec5 MatlabProgramming - Opinion Polls Physics 257 Lecture...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online