Title: Distance Learning Center
1Distance Learning Center
- Lecture 7
- Problem Solving with MATLAB
- Melissa Lin, IT Consultant
- HenEm, Inc. Parkville, Missouri
- linm_at_ipfw.edu
- http//www.etcs.ipfw.edu/linm
2Lecture 7 MATLAB Built-In Functions
- 7-1 Managing Variables and Workspace
- 7-2 MATLAB Commands for Working with Files and
the Operating System - 7-3 Controlling Command Window
- 7-4 Time and Date Functions
- 7-5 Special Variables and Constants
37-1 Managing Variables and Workspace
- Removing Unneeded Variables
- who - List current variables
- whos - List current variables, long form
- clear - Clear variables and functions
- Creating New Variables
- length - Length of vector
- size - Size of matrix
- Saving to and Retrieving from Disk Files
- load - Retrieve variables from disks
- save - Save workspace variables to disk
- pack - Consolidate workspace memory
- Workspace display
- disp - Display matrix or text
- fprintf
47-1 Managing Variables and Workspace (continue)
- Example 7-1
- cpet190_ex7_1.m
- F 4000
- T 1/F
- dt 0.01T
- t 0dt2T
- e1 5sin(2piFt)
- len length(e1)
- size_e1 size(e1)
- e2 zeros(size(e1))
- num rand(2)
fprintf('The random number array is g\n',
num) fprintf('\n') disp('The random
numbers') disp(num) whos save ex7_1 clear load
ex7_1 whos
57-1 Managing Variables and Workspace
67-2 Working with Files and OS
- The commands for working with files and operating
system - Command Purpose
- pwd Show present working directory
- cd Change current working directory
- dir Directory listing (Window OS)
- ls Directory Listing (Unix/Linux OS)
- delete Delete file
- diary Save text of MATLAB session
- ! Execute OS commands
77-2 Working with Files and OS
- Example 7-2 (cont.)
- gtgt diary
- gtgt diary off
- gtgt diary on
- gtgt !time
- The current time is 113105.02
- Enter the new time
- Open diary file using MATLAB M-file editor, MS
NOTEPAD, or MS Word - help
- Example 7-2
- gtgt pwd
- ans
- C\Courses\CPET190\matlabex190
- gtgt cd ..
- gtgt pwd
- ans
- C\Courses\CPET190
- gtgt dir
- . Mlin_CPET190
- .. Exs
- Quiz Lectures
- MATLABExs
87-3 Controlling the Command Window
- clc Clear command window
- home Send cursor home (upper-left corner
- of command window)
- format Set output format
- more Control paged output in command
- window
- echo Echo on/off commands inside script
- files, for debugging purposes
97-4 Time and Date Functions
- Function Purpose
- date Calendar
- clock System clock accuracy 1/100th of a second
- now Current date and time as serial date number
- datestr Convert a serial date number into the
common date/time, save as a string - cputime How many seconds the MATLAB session is
active accuracy 1/100 th of second - etime Elapsed time function
- tic Start watch timer function
- toc Stop watch timer function
107-4 Time and Date Functions
- Time and Date Functions
- Example 7-3
- gtgt date
- ans
- 03-Oct-2004
- gtgt now
- ans
- 7.3222e005
- gtgt datestr(now)
- ans
- 03-Oct-2004 124729
- gtgt help datestr
117-4 Time and Date Functions (continue)
- CLOCK Current date and time as date vector.
- CLOCK returns a six element date vector
containing the - current time and date in decimal form
-
- CLOCK year month day hour minute
seconds -
- The first five elements are integers. The
seconds element - is accurate to several digits beyond the
decimal point. - FIX(CLOCK) rounds to integer display format.
- Example
- gtgt clock
- ans
- 1.0e003
- 2.0040 0.0100 0.0030 0.0120
0.0410 0.0071
127-4 Time and Date Functions (continue)
- Example 7-4 measuring program execution time
(accuracy 1/100 th of a second) using cputime
function
t1_1 cputime for i 11000 num_array
inv(rand(30)) end t1_2 cputime time_1000
t1_2 - t1_1 time_once time_1000/1000
time_1000 0.3610 time_once 3.6100e-004
137-4 Time and Date Functions
- Example 7-5 measuring program execution time
(accuracy 1/100 th of a second) using tic and
toc functions
tic for i 11000 num_array
inv(rand(30)) end toc
elapsed_time 0.3610
147-5 Special Variables and Constants
- Example 7-6 AC circuit calculation using complex
numbers. - A RLC circuit is shown on this slide, find
- Total impedance Z
- Voltage and current across each components
157-5 Special Variables and Constants (continue)
- Example 7-6
- Analysis Domain knowledge
- XL 2pfL, where L is the inductance in Henry, f
is the frequency of ac source - XC 1/(2 pfC), where C is the capacitance in
Farard - Z R j(XL XC) -- total impedance, where j
shows the imaginary component of a complex number
- I E/Z, total current
- VR IR, voltage drop across resistor
- VL IXL, voltage drop across the inductor
- VC IXC voltage drop across the capacitor
167-5 Special Variables and Constants (continue)
- Example 7-6 MATLAB Program
- RLC_1.m
- f 60 R 8
- Peak value of the sine wave
- e 10
- XL j6 XC -j2
- Z R (XLXC)
- theta angle(Z) 0.4636 pi
- 180 pi
- ----- ----
- theta_degree theta
- theta_degree (180theta)/pi
- 26.5615 degree 0.4636 pi
- mag_Z abs(Z)
177-5 Special Variables and Constants (continue)
- Example 7-6
- MATLAB Program (cont.)
- RLC_1.m
-
- I e/Z
- I_thea_degree angle(I) (180)/pi
- I_mag abs(I)
- VR IR
- VL IXL
- VC IXC
- VR (VL VC) e 10 volt
- VR
- 8.0000 - 4.0000i
- VL
- 3.0000 6.0000i
- VC
- -1.0000 - 2.0000i
- gtgt VR (VL VC)
- ans
- 10
18Summary
- Managing Variables and Workspace
- MATLAB Commands for Working with Files and the
Operating System - Controlling Command Windows
- Date and Time Functions
- Special Variables and Constants
19Question?
- Answers
- Email linm_at_ipfw.edu