how to sparse represent a image?

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lohith
lohith 2014-12-27
评论： Snigdha KN 2017-1-26
hi,
i'm trying to create a sparse matrix for an image.
i've given the command as,
a=imread('imagename.format')
b=sparse(a)
i'm getting the output for the first command and for the second command i'm getting a error as mentioned below,
Undefined function 'sparse' for input arguments of type 'uint8'
please help thanks in advance

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Shoaibur Rahman
Shoaibur Rahman 2014-12-27
Convert a to double first, and the use that in sparse. Make sure that a is not in 3D, if so, then make it 2D before using in sparse.
a = double(a);
b = sparse(a); % for 3D a, you may use b = sparse(a(:,:,1)); or 2 or 3 instead of 1 here.
spy(b) % see the sparsity pattern
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Guillaume
Guillaume 2016-3-17
编辑：Guillaume 2016-3-17
@Isra, I suggest you start your own question posting the exact code you're using and explaining what 'not working' means exactly (you get an error? if so, which? no error but not the output you want? if so what output do you want? etc.)
Snigdha KN
Snigdha KN 2017-1-26
This code shows an error when executed. It shows undefined function 'sparse' for argument type 'double'

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