SUNY Geneseo Department of Computer Science

Introduction to Cell Arrays

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Questions?

How to save database?

• Via save command, exactly complementary to loading with load

    >> load database

    >> save newdatabase

Cell Arrays

Downloading database.mat file: if your browser tries to open the file instead of download it when you click on the link, try right-clicking and using “Download Link” command in resulting menu

In cell arrays, “tuple” = row

Cells vs content

• Unlike regular vectors and matrices, whose elements are, e.g., numbers, the elements in a cell array are “cells,” which are things that can in turn refer to a value somewhere else in computer memory
• Refering to elsewhere in memory allows the cell contents to be different types or sizes of data, even though the cells that make up the cell array are all the same type and size

• But you need 2 kinds of indexing, cell vs content, to indicate when accessing the array whether you want the cells or the things they refer to

    >> c = { 'Isaac Newton' 1666 }
    c = 
        'Isaac Newton'    [1666]
    >> c{2}
    ans =
            1666
    >> c(2)
    ans = 
        [1666]
    >> date = c{2}
    date =
            1666
    >> datecell = c(2)
    datecell = 
        [1666]
    >> datecell + 3
    Undefined function 'plus' for input arguments of type 'cell'.
    >> datecell{1} + 3
        ans =
            1669

• Beware that Matlab uses very subtle distinctions in how it prints results to distinguish cells from regular values
• The cellplot command can also be used to display the structure of a cell array through Matlab: