How to release zero elements in sparse matrix

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Jimmy
Jimmy 2013-2-7
Hi,
The Matlab document says sparse matrix does not release elements from memory when they are set to zero. Then how can I release the elements if they are zero?
For example:
>> a=sparse(ones(10,10));
>> nzmax(a)
ans =
100
>> a(1:5,1:5)=0;
>> nzmax(a)
ans =
100
>>
What I want is that nzmax(a) reports 75 since I don't want to waste the memory for 25 zeros. Is there any command I can use?
Thanks in advance!
Edit: Made the description of example clear.

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采纳的回答

Azzi Abdelmalek
Azzi Abdelmalek 2013-2-7
Your example is not correct, what you should do is
a=ones(10,10);
nzmax(a)
a(1:5,1:5)=0
a=sparse(a)
nzmax(a)

更多回答（2 个）

Andrei Bobrov
Andrei Bobrov 2013-2-7
nnz(a);
  1 个评论
Jimmy
Jimmy 2013-2-7
Hi Andrei,
Sorry I mean I want to really release the memory and that nzmax() reports 75. But thanks for the quick reply.
Jimmy

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Walter Roberson
Walter Roberson 2013-2-7
The examples of sparse show how to dissect and reconstruct a sparse matrix

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