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# How to correct the assignment Error?

Asked by PRIYANGA on 14 Dec 2012

I have to run the K-means clustering program using matlab.

```im = imread('D:\lena256.jpg');
k=5;
%histogram calculation
img_hist = zeros(256,1);
hist_value = zeros(256,1);
for i=1:256
img_hist(i)=sum(sum(im==(i-1)));
end
```

Run above code the following error occurred.

```??? In an assignment  A(:) = B, the number of elements in A and B
must be the same.
Error in ==> kmeansclustering at 10
img_hist(i)=sum(sum(im==(i-1)));
Error in ==> main at 5
[clusters, result_image, clusterized_image] = kmeansclustering(im,k);
```

How do I solve this problem?

José-Luis on 14 Dec 2012

Please edit your post. It makes it easier for people to understand your question, and shows a modicum of interest on your part.

Your problem is that

` img_hist(i) `

and

` sum(sum(im==(i-1)))`

are of different sizes.

Matt J on 14 Dec 2012

Incidentally, why not use HISTC to generate the histogram? Why re-invent that wheel with for-loops?

PRIYANGA on 14 Dec 2012

ok Sir I have to try.

## Products

Answer by José-Luis on 14 Dec 2012

Try

` img_hist(i)= sum(sum(sum(im==(i-1))));`

im might be a three dimensional matrix.

PRIYANGA on 14 Dec 2012

Thank You So Much Sir. Its working

José-Luis on 14 Dec 2012

My pleasure, but please edit your posts for clarity in the future.

Answer by Jürgen on 14 Dec 2012

Hi,

there is a function: imhist(I) , quite useful for this work, + if you want to calculate the hist by summing for each value 0=>255 you will get a array with a lenght of 256 not 256*256

regards,J

## 1 Comment

Jürgen on 14 Dec 2012

and indeed the comment of JL above is also a good point: the image could be a (VertRes, HorRes,3) matrix