Lecture 2MATLAB fundamentals

Variables, Naming Rules, Arrays (numbers, scalars, vectors, matrices), Arithmetical Operations,Defining and manipulating arraysVariablesWhat are variables?You name the variables (as the programmer) and assign them numerical values.
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Lecture 2MATLAB fundamentals Lecture2 Lecture2 MATLABfundamentals Variables,NamingRules, Arrays(numbers,scalars,vectors,matrices), ArithmeticalOperations, Definingandmanipulatingarrays© 2007 Daniel Valentine. All rights reserved. Published byElsevier. Variables Variables Whatarevariables? – Younamethevariables(astheprogrammer) andassignthemnumericalvalues. VariableNamingRules VariableNamingRules MustbeginwithaLETTER Mayonlycontainletters,numbersand underscores(_) Nospacesorpunctuationmarksallowed! Onlythefirst63charactersaresignificant; beyondthatthenamesaretruncated. Casesensitive(e.g.thevariablesaandA arenotthesame) Whichvariablenamesare Whichvariablenamesare valid? 12oclockRock tertiarySector bluecows Eiffel65 red_bananas This_Variable_Name_Is_Quite_Possibly_Too_L ong_To_Be_Considered_Good_Practice_Howev er_It_Will_Work%(thegreenpartisnotpartof therecognizedname) VariableNamingConventions VariableNamingConventions Therearedifferentwaystonamevariables.The followingillustratesomeoftheconventionsused: – lowerCamelCase – UpperCamelCase – underscore_convention Ifavariableisaconstant,someprogrammersuseall caps: – CONSTANT Itdoesnotmatterwhichconventionyouchoosetowork with;itisuptoyou. Variables as ArraysIn MATLAB, a variable is stored as an array of variablenumbers. When appropriate, it is interpreted as ascalar, vector or matrix.scalar vector matrix scalar vector matrix 1×1 n × 1 or 1 ×n n×mThe size of an array is specified by the number ofTherows and the number of columns in the array, withthe number of rows indicated first.the Scalars Scalarsare1×1arrays. Theycontainasinglevalue,forexample: r=6 height = 5.3 width = 9.07 Vectors Vectors A vector is a list of numbers expressed as a 1 vector dimensional array. dimensional A vector can be n×1 or 1×n. Columns are separated by commas (or spaces): Columns commas h = [1, 2, 3] Rows are separated by semicolons: Rows semicolons v = [1; 2; 3] Matrices Columns 1 2 3 Amatrixisatwo 1 3.0 1.8 3.6 dimensionalarrayof numbers. 2 4.6 2.0 21.3 Rows 3 0.0 6.1 12.8 Forexample,thisisa 4×3matrix: 4 2.3 0.3 6.1m = [3.0, 1.8, 3.6; 4.6, -2.0, 21.3; 0.0, 2.0,-6.1, 12.8; 2.3, 0.3, -6.1] 6.1,Indexedlocationofnumbersinan array Columns Eachiteminanarray 1 2 3 islocatedinthe (row,column). 1 3.0 1.8 3.6 m(2,3) m(2,3) 2 4.6 2.0 21.3 Rows ans = ans 21.3000 21.3000 3 0.0 6.1 12.8 4 2.3 0.3 6.1 Examples EnterthefollowingintoMATLAB: – Scalar: a=1 – Vectors: b = [1, 0, 2] c = [1 0 2] – Matrix: d = [5, 4, 3; 0, 2, 8] Examples Examples Enter(input)thefollowingmatrixintoMATLAB: 7 21 6 2 32 0 whiteRabbit = 5 0 18.5ScalarOperationsScalarOperationsOperation Algebraic MATLAB Syntax Syntax a+b a+b Addition ab a–b Subtraction a×b a .* bMultiplication a÷b a ./ b Division ab a .^ bExponentiation ArrayOperations ArrayOperations ArraysofnumbersinMATLABcanbeinterpretedas vectorsandmatricesifvectorormatrixalgebraistobe applied.Recallthatmatricesaremathematicalobjects thatcanbemultipliedbytherulesofmatrices.Todo matrixmultiplication,youneedtousethestandard*,/, and^ operators[withoutthepreceding.(dot)].Theyare operators[withoutthepreceding notforarraymultiplication,divisionandexponentiation. Todealwitharraysonanelementbyelementlevelwe needtousethefollowingarrayordotoperators: .* ,./ .^ .* ./ and and Arrayoperations&dotoperators Arrayoperations&dotoperators .*,./ .^ ./ and and Becausescalarsareequivalenttoa1×1 array,youcaneitherusethestandardor thedotoperatorswhendoing multiplication,divisionandexponentiation ofscalars(i.e.,ofsinglenumbers). Itisokayforyoutoalwaysusethedot operators,unlessyouintendtoperform vectorormatrixmultiplicationordivision. ...