Cell Arrays

Return to List of Lectures

Previous Lecture

• Misc
  • Calculus Bee
    • April 23 (tomorrow), 4:00 - ?
    • Newton 203
• Questions?
• Cell Arrays
  • Cell arrays vs ordinary arrays
    
  • Section 8.1
    • Can store different types in cells
    • Create with curly braces (not square)
      • Columns separated by spaces, commas
      • Rows by semicolons
    • celldisp function to display elements
    • cellplot draws diagram
    • Cell indexing accesses first-level cells
    • Content indexing accesses second-level user-meaningful data
  • Examples
    • Try to make a vector/matrix containing strings ‘hello’ and ‘cat’
      • It has to be a cell array because strings are really arrays of characters
        

        >> V = [ 'hello' 'cat' ]
        V =
        hellocat
        >> V2 = { 'hello' 'cat' }
        V2 = 
            'hello'    'cat'
        >> W(1) = 'hello'
        {Subscripted assignment dimension mismatch.} 
        >> S = 'hello'
        S =
        hello

    • Concatenate ‘aardvark’ onto it
      • Be careful to use content indexing because ‘aardvark’ is second-level content, not a first-level cell
        

        >> V2{3} = 'aardvark'
        V2 = 
            'hello'    'cat'    'aardvark'
        >> size(V2)
        ans =
            1     3
        >> V2(4) = 'wombat'
        {Conversion to cell from char is not possible.} 

    • Make a table of item names and prices; do some things with it
      

      >> prices = { 'computer' 500; 'water' 1.95 }
      prices = 
          'computer'    [   500]
          'water'       [1.9500]
      >> prices{1,2}
      ans =
          500
      >> prices(1,2)
      ans = 
          [500]
      >> class( prices{1,2} )
      ans =
      double
      >> class( prices(1,2) )
      ans =
      cell
      >> size( prices(1,2) )
      ans =
          1     1
      >> prices(3,:) = { 'music' [0.99 1.29] }
      >> prices = 
          'computer'    [       500]
          'water'       [    1.9500]
          'music'       [1x2 double]
      >> prices{3,2}(1)
      ans =
          0.9900

  • Lab 8
    • Handout
• Next
  • Saving and loading Matlab data to/from files
  • Read section 9.3

Next Lecture