Cell Array indexing and manipulating

The following code is entered in the command window:

A = {'Cal', 'Golden', 'Bears', [5 7], {[1 2 3 4]}};

Enter a single-line command the extract the number 3 from A

A{5}{1}(3)

Hello, I am confused about this problem. Why wouldn't the answer be A{5}{3} ??

[Image Analyst]

Have you read the FAQ: http://matlab.wikia.com/wiki/FAQ#What_is_a_cell_array.3F It should give you an intuitive appreciation for cell arrays.

Answer 1

[Geoff Hayes]

Rick - try the code in steps. Start with

 A{5}

The above returns the fifth element of the cell array A as

 ans = 

    [1x4 double]

But what is the data type and size? Try

 class(A{5})

    ans =
        cell

 size(A{5})

    ans =
     1     1

So it is a 1x1 cell array. So trying to use

 A{5}{3}

will result in the Index exceeds matrix dimensions error as 3 is not a valid index into the 1x1 cell array. Now try

 A{5}{1}

and determine its type and dimension as

 class(A{5}{1})

   ans =
     double

 size(A{5}{1})

   ans =
     1     4

It is a 1x4 array of doubles, and so we can access the 3 as

 A{5}{1}(3)

Note in the above how we use the curly braces {} for cell arrays, and brackets () for non-cell arrays.

Answer 2

[Andrei Bobrov]

A = {'Cal', 'Golden', 'Bears', [5 7], {1 2 3 4}};

A{5}{3}

or

>> A = {'Cal', 'Golden', 'Bears', [5 7], [1 2 3 4]};
>> A{5}(3)
ans =
     3
>>

[Rick]

You misunderstood the premise. I can't change what A is. I am supposed to extract 3 from A exactly the way it is. I was wondering why it is A{5}{1}(3)