Strings

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• Misc
  • Colloquium
    • Brendan Murphy, U of R and Geneseo alumnus
    • “The Sum-Product Problem”
    • Wednesday, April 27, 2:45 - 4:00, Newton 204
    • Extra credit as usual for write-ups
  • Final
    • Friday, May 6, 8:00 AM
    • In our classroom
    • Comprehensive, but emphasizing material since 2nd hour exam (e.g., vectorization, 3D arrays, images, cell arrays, strings, files, etc.)
    • Designed for 2 hours, you’ll have 2 1/2 +
    • Rules and format similar to hour exams
    • Donuts and cider
  • SOFIs
    • Helpful to me in planning future offerings of this course, especially comments on text
    • 6 filled out so far!
    • But please fill out more
• Questions?
• Madlibs Project
  • Handout
  • Demonstration
    • A very important part of this project is that you devise a way to represent a mad lib in Matlab, e.g., as a matrix, string, cell array, number, or some other data type that Matlab has.
    • You need to be able to store mad libs that use that representation in Matlab variables and pass them as arguments to your mad lib function.
    • A function that just has one (or some other fixed number) of mad libs built in to it is not what I expect in this project.
• Questions?
• Strings
  • Sections 8.1 through 8.4
    • String = sequence of characters between single quotes
    • Characters are values from char class
    • Whitespace characters: invisible but used for formatting
      • e.g., space, tab, newline, etc.
    • Can make sentences using strings
    • blanks function adds blanks between strings, avoids typing hard-to-see space character
    • Character properties
    • There are built-in functions on strings that return logical arrays based on character properties
    • Can do case-sensitive comparison of strings
    • Also functions to remove whitespace, flush left, etc.
    • Discussion of string parsing, i.e., breaking them up, manipulating
      • Indexing breaks strings up, i.e., picks parts out of a string
    • Also search and replace functions
  • Examples
    

    >> % Create some strings
    >> s = 'This is a string'
    s =
    This is a string
    >> size( s )
    ans =
         1    16
    >> s2 = 'So is this'
    s2 =
    So is this
    >> % Concatenate strings
    >> [ s, s2 ]
    ans =
    This is a stringSo is this
    >> [ s, blanks(1), s2 ]
    ans =
    This is a string So is this
    >> % Pick a substring out of a string
    >> s( 6:7 )
    ans =
    is
    >> % Is s equal to "hello world"?
    >> strcmp( s, 'hello world' )
    ans =
         0
    >> s == 'hello world'
    Error using ==
    Matrix dimensions must agree.

    • Notice how comparing strings requires strcmp or a related function to avoid unhelpful and often impossible element-by-element vector comparison
• Database Lab
  • You can open the downloaded “database.mat” file into Matlab when you download it, but this is tedious if you re-download every time you want to use the database
    • I recommend that you download it once to your own computer, put it in the folder where you are working on this lab, and then use load in the Matlab command window (or a script) to load it into Matlab
  • Matlab also has a neat little cell array inspector/editor that opens up if you double click on a cell array in Matlab’s workspace pane
• Next
  • Database lab day
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