VIEWS: 7 PAGES: 5 POSTED ON: 8/31/2012 Public Domain
Matlab Introduction This lecture notes deal with Matlab version 6.5 on windows environment. It should be backward compatible with older versions. Matlab is a registered trademark of MathWorks, Inc. Let us introduce Matlab in windows environment. Its front-end (Graphical user interface) is very easy to use and is user friendly. Further it is compatible with standard windows applications and supports 1) File operations 2) Multiple windows view. 3) help, demos and example (Check whether this component is installed) 4) Wizard to create a GUI (graphical user interface) 5) Wizard to profile code 6) Toolboxes for different components like communication, control systems, data acquisition, curve fitting, fuzzy logic, neural network etc. (These components may or may not be available, depending upon the installation) 7) simulator libraries (Not to be discussed now) When matlab application is started, it looks like figure 1. Figure 1: Matlab command window CURRENT DIRECTORY MENU COMMAND COMMAND WORKSPACE TOOLBOX 1 HISTORY WINDOW MENU WINDOW & WINDOW CURRENT DIR WINDOW WITH 2 TAB VIEWS (current directory/workspace) WINDOW PURPOSE Command Window To enter commands Command History Window To see previous commands Workspace window Provide information about the variables that are used Current Directory Window Shows the files in current directory Launch pad window (Toolbox Menu) Provide access to tools and demos Table 1: Description of common windows There are other windows of matlab, which are equally important. Table 2 describes them in brief and will be introduced later. WINDOW PURPOSE Help window Provides Help information Editor window Text editor to write programs Figure window Output of Graphical commands Table 2: Description of other windows Exercise 1 To use Matlab as a calculator Matlab can be used as a calculator. In the command window start typing simple examples The following can be observed -: 1) To type a command cursor must be placed next to command prompt, (>>). 2) Several commands can be typed in the same line with comma separating the commands. If comma is missed then only the last command is executed 3) Semicolon (;) is used to suppress the output (No output is echoed on the screen) 4) Percentage (%) is used as comments 5) clc is used for clearing screen (It is same as cls in windows command prompt or clear in unix shell) 6) Addition (+), Subtraction (-), multiplication (*), exponent (^), Division --- right & left is supported. Normal division is known as right division (/) ex 4/2 =2. Left division (\) ex 4\2= 0.5 7) If a command is too long to fit in one line, it can be continued by typing three periods (…) called ellipsis and pressing the enter key 8) Numerous display formats are supported. They are invoked by typing format xxxx, on the command prompt, where xxxx can stand for numerous things. More information can be obtained by typing help format on the command prompt. The various display formats are shown in table 3. Please fill in the description column of Table 3 by practically carrying out the examples. 2 COMMAND DESCRIPTION EXAMPLE format short >>290/7 ans = 41.4286 format long >>290/7 ans = 41.42857142857143 format short e >>290/7 ans = 4.1429e+001 format long e >>290/7 ans = 4.142857142857143e+001 format short g >>290/7 ans = 41.429 format long g >>290/7 ans =41.4285714285714 format bank >>290/7 ans = 41.43 format compact format loose Table 3 : Output format options 9) Carry out the exercise in table 4 to use matlab as a calculator, use format long -: COMMAND ANSWER >>7 + 8/2 >>7+8\2 >>(7+8)/2 >>4 + 5/3 +2 >>5^3/2 >>5^(10/5) >>27^(1/3) + 32^0.2 >>27^1/3 + 32^0.2 >>0.7854 -(0.7854)^3/(1*2*3) + ... 0.785^5/(1*2*3*4*5) - … (0.785)^7/(1*2*3*4*5*6*7) Table 4: Matlab as calculator 10) Has predefined Mathematical symbols. pi, inf, i; defined for , , square root of (-1). 11) Elementary Math Build in functions, table 5 . Carry out the examples and fill in the answers use format short -: FUNCTION DESCRIPTION EXAMPLE sqrt(x) Square root >>sqrt(82) ans = x exp(x) Exponential (e ) >>exp(5) ans = abs(x) Absolute Value >>abs(-24) 3 ans = log(x) Natural Logarithm. Base e >>log(1000) logarithm (ln) ans = log10(x) Base 10 logarithm >>log10(1000) ans = factorial(x) The Factorial function, x must >>factorial(5) be positive ans = sin(x) Sine of an angle x, x in >>sin(pi/6) radians ans = cos(x) Cosine of an angle x, x in >>cos(pi/6) radians ans = tan(x) Tangent of an angle x in >>tan(pi/6) radians ans = cot(x) Cotangent of an angle x in >>cot(pi/6) radians ans = round(x) Round to nearest integer >>round(17/5) ans = fix(x) Round towards zero >>fix(13/5) ans = ceil(x) Round towards infinity >>ceil(11/5) ans = floor(x) Round towards minus infinity >>floor(-9/4) ans = rem(x,y) Returns the remainder after x >>rem(13,5) is divided by y ans = sign(x) Signum function. Returns 1 if >>sign(5) x>0, -1 if x <0 and 0 if x =0. ans = Table 5 : Elemenatry Mathematical functions In addition to the above mentioned functions matlab supports inverse trigonometric functions [asin(x), acos(x), atan(x) and acot(x)] and hyperbolic trigonometric functions [sinh(x), cosh(x), tanh(x), coth(x)]. Defining Scalar Variables In Matlab, a variable can be declared using a variable name. The syntax for declaring a scalar variable is variable_name = A numerical value, or a computable expression, or a previously defined variable name. ex: >>x =15 >>a=12 Rules about Variable Names -: 1) Can be 63 characters long (matlab version 6.5, version 6.0 allows for 31 characters) 4 2) Can contain letters, digits and underscore characters. 3) Must begin with a letter. 4) Should not be defined to predefined mathematical symbols (pi, inf, i, j , Nan, ans ,eps). One should avoid names of built-in functions. Useful commands for managing variables. Some useful commands for managing variables are mentioned in table 6 COMMAND OUTCOME clear Remove all variables from the memory. clear x y z Remove only variables x, y, z from the memory who Display a list of the variables currently in the memory whos Display a list of the variables currently in the memory and their size together with information about bytes and class. 5