MATLAB: How to create a method which takes an excel file as an argument in a constructor

MATLABmethod argumentsobject-orientedpassing files through arguments

Basically, I'm trying to construct a method that allows users to input a data file. It can be excel or ascii, and the method reads it as a matrix which can then be tested on.

Here is some of the rudimentary code I've modified from the tutorial:

classdef BankAccount < handle
  properties (Hidden)
      AccountStatus = 'open';
  end
    properties (SetAccess = private)
        VEC
        AccountBalance = 0;
    end
    events
        InsufficientFunds
    end
    methods
        function BA = BankAccount(filename, InitialBalance)
            BA.VEC = xlsread(filename);
            BA.AccountBalance = InitialBalance;

then I try: BankAccount('sample.xlsx',55)

I'm getting an error: No public field VEC exists for class BankAccount.

Error in BankAccount (line 20) BA.VEC = xlsread(filename);

Best Answer

My guess is that it has nothing to do with the fact that you want to read an xls file.

If you really have the code that you gave above, with 3 additional end at the end and nothing else like setters/getters or overloads of subsasgn/subsref, i.e.:

 classdef BankAccount < handle
    properties (Hidden)
       AccountStatus = 'open';
    end
    properties (SetAccess = private)
       VEC
       AccountBalance = 0;
    end
    events
       InsufficientFunds
    end
    methods
       function BA = BankAccount(filename, InitialBalance)
          BA.VEC = xlsread(filename);
          BA.AccountBalance = InitialBalance;
       end
    end
 end

then the error..

Could be related to something new in R2012a that I will discover in less than 2 weeks according to my license manager ;-)
Could come from a upper/lowercase mismatch between the declaration of properties and the constructor (like BA.VEc=.., that I don't observe in what you pasted actually).
I am unsure whether the editor would allow that, but could you have some sort of invisible special character that came during the copy-paste that you probably made from the PDF manual about OOP in MATLAB?

You could perform a few checks actually. Try replacing

 BA.VEC = xlsread(filename);

with

 BA.VEC = [] ;

so you eliminate anything related to xls stuff. If it still generates an error on VEC, try commenting the line and see it is specific to VEC or if it happens as well with AccountBalance.

You could also comment out the events block and avoid subclassing handle, to see if the issue comes from some conflict with handle methods/properties..

 classdef BankAccount %< handle
    ...
    %events
    %   InsufficientFunds
    %end
    ...

Cheers,

Cedric

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MATLAB: OOP in Matlab: input arguments for methods other than constructor

"BA.withdraw(600) instead of BA.withdraw(BA,600)."

There are two alternative ways to call a method

    withdraw( BA, 600 )

and

    BA.withdraw( 600 )

(remember BankAccount is a handle class).

"Why does the object have to be the first input argument?" &nbsp and &nbsp " Why is that?" &nbsp I have no better answer than: At The Mathworks they decided on that syntax. However, there is a function, why :-)

See Comparing MATLAB with Other OO Languages

MATLAB: How do you create a matrix of matrices in a method

Leaving aside OOP, we can say the following:

In your code, FI should be BA (the object) and you should replace Index=zeros(30); with Index=cell(30,1); to create a cell array, and then replace

 BA.Index(FI.IndicatorCount)= FI.VEC ;

with

 BA.Index{BA.IndicatorCount}= BA.VEC ;

Then you should type

 >> doc cell

in your command window and read a bit about cells and cell arrays, and maybe also have a look at my answer there: http://www.mathworks.com/matlabcentral/answers/58977-is-used-as-index-array-in-class so you have a better understanding of cell arrays.

Now about OOP

You cannot implement the code that adds elements to BA.Index in the constructor (method BankAccount), because it will be called only once when the class is instantiated (when the object is created). What you should have is a constructor that initializes relevant properties, and additional methods that can be called to perform actions, like adding/updating data/properties. For example:

 properties
    accountsCounter
    accounts
 end
 methods
    function obj = BankAccount( filename )    % Constructor.
       obj.accountsCounter = 0 ;
       obj.accounts = cell( 30, 1 ) ;         % Prealloc for 30 accounts.
       if nargin
          obj.add( filename )
       end
    end
    function add( obj, filename )
       obj.accountsCounter = obj.accountsCounter + 1 ;
       obj.accounts{obj.accountsCounter} = xlsread( filename ) ;
    end
 end

With that you can create an account or not when you create the object:

 >> ba = BankAccount() ;

 >> ba = BankAccount( 'JohnDoe.xlsx' ) ;

And then add accounts using the add() method:

 >> ba.add( 'MrSmith.xlsx' ) ;

.. and you can access "manually" properties just to check the functioning:

 >> ba

 >> ba.accounts{1}

Best Answer

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