Converting cell array to matrix

I was doing my project on huffman coding on a gray scale image. I have three arrays

1. code
2. level_of_gray
3. length_of_code

>> whos code

Name        Size            Bytes  Class    Attributes

code      256x1             33374  cell

>> whos level_of_gray

Name                 Size            Bytes  Class     Attributes

level_of_gray      256x1              2048  double

>> whos length_of_code

 Name                 Size            Bytes  Class     Attributes
length_of_code      256x1              2048  double

each cell of(code) has characters(strings of 0's and 1's upto length 16)

I want to make a code_dictionary=[level_of_gray;length_of_code;code]

but MATLAB is not allowing to do it. I have tried cell2mat (code). But this is also not working.

[Andrew Newell]

Do you want to leave the codes as character representations of binary numbers?

[Manisha Mehra]

yes

[Walter Roberson]

You cannot leave the codes in character representation if you want to form a numeric array. Only cell arrays can contain a mix of numbers and characters.

[Manisha Mehra]

exactly,I don't need a numeric array.

Thanks

Answer 1

[Walter Roberson]

code_dictionary = [num2cell(level_of_gray),  num2cell(length_of_code), code]

This will produce a 256 x 3 cell array.

Trying to convert your code cell to matrix form is not going to work because your codes are variable length. In order to put them in to matrix form, you would have to make them all the same length, such as by padding the shorter ones with values other than 0 and 1 that the rest of your code would have to know to detect and throw away.

So what you could do is:

code_dictionary = [level_of_gray, length_of_code,
cell2mat(cellfun(@(V) [V - '0', nan(1,16-length(V))], code, 'Uniform', 0)))];

This would produce a 256 x (2+16) matrix of doubles. The first column would be the gray level, the second column would be the code length, and the 3rd to 18th columns would be the values of the code, with '0' and '1' transformed to 0 and 1, and with NaN values in all unoccupied places.

[Manisha Mehra]

Thanks for the reply.

I think the first method is perfect for me as I don't want to convert my code array to numbers. It will make my code lengthy.

I have one more doubt.

I am going to pass this code_dictionary in huffman_encoding function.

But in that function I again need length_of_code and code as two separate arrays.

Is there any way to call them by their array name or I have to again assign variable to code_dictionary{1:256,1}and so on.

[Walter Roberson]

There will be no way to call them by their array names.

level_of_gray = vertcat(code_dictionary{:,1});

code = code_dictionary(:,3);

[Manisha Mehra]

thanks you so much