March R. Smith - University of St Thomas - Minnesota Today’s Class Class StuffClass Stuff ProjectProject Vectors and DimensionsVectors and Dimensions Import/Export of numerical matricesImport/Export of numerical matrices Working with parts of matricesWorking with parts of matrices Scripts (shell scripts)Scripts (shell scripts)

March R. Smith - University of St Thomas - Minnesota Class Stuff Exam schedulesExam schedules –How many people need to switch exam days? Potential extra credit ‘quiz’Potential extra credit ‘quiz’ –Writing functions and such

March R. Smith - University of St Thomas - Minnesota Project Project StorageProject Storage –I’ll set up shared space for each group project Project PlanProject Plan –Behavior – a paragraph on what the project does –Choices – a summary of choices the user can make –Activities – a list of things the program must do You will probably build one function per activityYou will probably build one function per activity These can be broken into more functions if you wantThese can be broken into more functions if you want –Source Files – list of source files and what activities are in each –Assignments* – which project member works on which file –Files* – description of data files (input or output) you use * = optional, appears if relevant

March R. Smith - University of St Thomas - Minnesota A Course Objective Writing functions and solving problems in both C and MatlabWriting functions and solving problems in both C and Matlab To do this, you must understand the features of each languageTo do this, you must understand the features of each language You should be able to write a simple function (with loops and conditionals) in both.You should be able to write a simple function (with loops and conditionals) in both.

March R. Smith - University of St Thomas - Minnesota Vectors in Matlab Count 1 to size, not 0 to size-1Count 1 to size, not 0 to size-1 No “declaration” – just initialize and useNo “declaration” – just initialize and use –Easy to add and remove elements, NOT like C Square Brackets for the contentsSquare Brackets for the contents –elmstreet = [ ] –No commas required –Curly braces & commas in C: int x[] = {1, 4, 2, 66, 5}; Parentheses for index valuesParentheses for index values –Like arguments to functions in Matlab or C –Square brackets in C for index values: name[i][0] –Comma separated list in Matlab: name(i, 1)

March R. Smith - University of St Thomas - Minnesota Working with vectors Addressing: first element = 1Addressing: first element = 1 –Last element: “end” Addressing some elements: foo([1 2 5])Addressing some elements: foo([1 2 5]) Adding to a vector: foo = [foo, 2, 3]Adding to a vector: foo = [foo, 2, 3] –or: foo(end+1) = 3 –Fibonacci Removing: foo(2:3) = []Removing: foo(2:3) = [] Functions on vectorsFunctions on vectors –sum, mean, max, length –find -> list of indices of non-false (non 0) elements

March R. Smith - University of St Thomas - Minnesota Boolean vectors Created with logical operatorsCreated with logical operators –x = foo > 3 –x contains 1s and 0s for elements of foo that are >3 –Can say foo(x) to create a vector of just those elements A ‘special’ kind of vectorA ‘special’ kind of vector Not just any vector of 1s and 0s.Not just any vector of 1s and 0s. Find functionFind function –Takes boolean vectors –Also takes any vector with 0s and non-0s logical functionlogical function –Converts vector of 0s and non 0s to a boolean vector

March R. Smith - University of St Thomas - Minnesota Vectors versus Function Names Both C and Matlab are stupid about thisBoth C and Matlab are stupid about this –But each in their own way What happens in C?What happens in C? –Declare a function named ‘min’ –Declare a variable named ‘min’ What happens in Matlab?What happens in Matlab? –There is a function named ‘sqrt’ –What if there is a vector named ‘sqrt’ ? –Say, sqrt = [ ] –sqrt (4) is 4!

March R. Smith - University of St Thomas - Minnesota Some Vector Exercises Sorting – [x,y] = sort(vec)Sorting – [x,y] = sort(vec) Randomness – rand(size(vec))Randomness – rand(size(vec)) Use colon to pick even valuesUse colon to pick even values IndicesIndices –Use modulus to pick even indices –Partial index lists –Negative Index lists

Assignment Write a lot of expressionsWrite a lot of expressions Answers should be expressions in terms of variables, not just numerical answers!Answers should be expressions in terms of variables, not just numerical answers! March R. Smith - University of St Thomas - Minnesota

March R. Smith - University of St Thomas - Minnesota Scripts Just save a series of Matlab commands in a fileJust save a series of Matlab commands in a file Give it a.m suffixGive it a.m suffix Refer to it by name inside Matlab as a ‘command’Refer to it by name inside Matlab as a ‘command’ Use % as comment marker (like //)Use % as comment marker (like //) Functions are different – we’ll get to that laterFunctions are different – we’ll get to that later

March R. Smith - University of St Thomas - Minnesota Import/Export of Matrices New population vectorNew population vector –Row 1 = #people in a house –Row 2-5 = four highest ages of people in a house Using Excel to type in a matrixUsing Excel to type in a matrix Using TextpadUsing Textpad Importing/ExportingImporting/Exporting –x = importdata(‘file.txt’); –x = csvread(‘file.csv’); –csvwrite(‘file2.csv’, x);

March R. Smith - University of St Thomas - Minnesota Parts of Matrices Try town(:,1), town(1,:), town(2:end,:)Try town(:,1), town(1,:), town(2:end,:)

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