Error using huffman code

I get error 

Error using ==> huffmandict at 72
The symbol input must be a vector

Error in ==> Untitled3 at 5
[dict,avglen]=huffmandict(symbols,p)

wen using the code 

A=imread('lena.jpg');
A=rgb2gray(A);
[symbols,p]=hist(A,double(unique(A)));
p=p/sum(p)
[dict,avglen]=huffmandict(symbols,p)
comp=huffmanenco(A,dict)

please help

Answer 1

[Walter Roberson]

Remember that hist() applied to an array (rather than a vector) histograms by column. This behavior is not documented, though: what is documented is that you must hist() a vector.

[kash]

id i use A(:),will it be correct

[kash]

if i use A(:) i get error as

Error using ==> huffmandict at 174 Source symbols repeat

Error in ==> Untitled3 at 6 [dict,avglen]=huffmandict(symbols,p)

[Walter Roberson]

Yes, but your problem with symbols needing to be a vector is solved.

I am not surprised that your symbols repeat. I would rather expect that when you use counts as the symbols.

[kash]

can u please correct the code above

[Walter Roberson]

You should be passing a vector of symbols at that point. And the p vector should be the vector of the probabilities of each symbol.

I cannot correct the code for you because you need to decide which symbols you are going to use. Symbols can be intended to represent different numbers of bits. For example if you often had 10 consecutive 0 bits, then it might be worth creating a symbol for that.

[kash]

ok walter is there any solution for encoding using huffman encoding

[kash]

i used a code in 

http://www.mathworks.in/matlabcentral/answers/2158

but i get error 

In an assignment  A(I) = B, the number of elements in B and
 I must be the same.

Error in ==> Untitled4567 at 18
      count(j) = c;

[Walter Roberson]

The "solution" is for you to decide which symbols you are going to use, and calculate the appropriate probabilities. Just like I could tell you that there is a special on "Liver and Brussel Sprouts", but you need to decide for yourself what you want to order off the menu.

[kash]

Acutually walter its image copmresiion,i have performed dwt2,want to compress cA,cH bands

[Walter Roberson]

So you are indicating to me that you want to have exactly two symbols, 'cA' and 'cH' ?

huffmandict({'cA', 'cH'}, p)

[kash]

i get same eerror

Error using ==> huffmandict at 97 The symbol and probability vector must have the same length

Error in ==> Untitled28 at 13 [dict,avglen]=huffmandict({'cA', 'cH'}, p);

[Walter Roberson]

I think you should go back and study the theory about what a "symbol" is for the purposes of huffman encoding.