Looping problem need guide.

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reez all 2012-2-24

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此问题的直接链接

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编辑： Cedric 2013-10-23

how to use loop that the number of edges for output is equal as the input for the coding below:

clear;
clc;
nodes=6;
edges=8;
cnt = 0;
DG = zeros(nodes);
ancs = zeros(nodes); % matrix of ancestors
childs = zeros(nodes); % matrix of children
for e=1:edges
  i=randi(nodes-1,1); % source node for new edge
  j=randi([i+1,nodes],1); % target node for new edge
  if sum(sum(DG(logical(ancs(j,:)),logical(childs(i,:)))))==0 && ...
     sum(sum(DG(logical(ancs(i,:)),logical(childs(j,:)))))==0 && ...
     sum(DG(logical(ancs(i,:)),j))==0 && sum(DG(i,logical(childs(j,:))))==0
     % add edge
     DG(i,j)=1;
     % update ancestor and children relationship in the graph
     ancs(j,i)=1;
     ancs(j,:)=ancs(j,:)|ancs(i,:);
     childs(i,j)=1;
     childs(i,:)=childs(i,:)|childs(j,:);
  end
end
edge=sum(sum(DG));
disp(edge);

i try to use while loop but still not work correctly. thank you.

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Jan 2012-2-24

@Reez all: Please do not send me emails. I answer every question I can answer. Trying to push me by emails does decrease my motivation to even read a question. Thanks.

It you really think that contacting the contributors directly is helpful, be sure to add a link to the question in your mail.

reez all 2012-2-24

I apologise. I'm just think that you can help me because i see that you have wide knowledge related to the matlab. Sorry for interrupting you.

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Answer 1

Geoff 2012-2-24

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在 MATLAB Online 中打开

So you mean that you want the number of 1's in DG to be equal to edges?

I would say that if-condition is preventing some edges from being added, and you are assuming by looping from 1:edges that it will be satisfied every time. Your two calls to randi do not guarantee that the same edge has not already been added. You say you used a while-loop... Was it similar to the following?

while sum(DG(:)) < edges
  ....
end

That would guarantee the end-result that you seem to be looking for. If the loop never terminates, then there is bound to be a problem with the logic in the if, which looks more convoluted than perhaps it needs to be.

-g-

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reez all 2012-2-24

thank you for your help, yes i need the number of 1's in DG to be equal to edges. i also have use the while loop that similar with the following code and as result the loop never terminates.

do you have any suggestion to improve my 'if' condition so that it can generate the same result?? The 'if' condition is full fill the Partially ordered set which is the main objective of my code. im really appreciate if you can help me to repair this code.

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