programming to find out all possible combination of numbers a,b,c,d in which 0<a<b<c<d<90.

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UJJWAL BARMAN 2015-8-26

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回答： UJJWAL BARMAN 2015-9-5

采纳的回答： Guillaume

all possible combination of numbers a,b,c,d in which 0<a<b<c<d<90.

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Guillaume 2015-8-26

You have to clarify what you mean by numbers. There is of course an infinity of numbers between 0 and 90. Do you mean integers?

UJJWAL BARMAN 2015-8-26

I only want to get the integer values.the program will just have to deal with 1,2,3,4,..upto 89 these values only.The output will be like this. a=1 b=2 c=3 d=4 and goes on just only follow the condition that 0<a<b<c<d<90. I want all the possible combination.

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Guillaume 2015-8-26

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编辑：Guillaume 2015-8-26

在 MATLAB Online 中打开

Isn't this simply four for loop?

for a = 1:86
  for b = a+1:87
    for c = b+1:88
      for d = c+1:89
         %do whatever you want with a,b,c,d
      end
    end
  end
end

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UJJWAL BARMAN 2015-9-4

i want all the combination in output but it is giving only the last combination output i.e a=86,b=87,c=88,d=89.

Walter Roberson 2015-9-4

Be specific about how you want them output. Do you want them all displayed? If so then is a list of 4 numbers per line acceptable? Do you need every line to include the text 'a=' and ',b=' and so on? Do you want a variable that contains a something-by-4 array where each line is an a, b, c, d selection?

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Walter Roberson 2015-8-26

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There will be 4636033603912859644 choices for "a" alone, for a total of 19247532396881346240525890574203961674141911582083171582958740223586992125 combinations. That is roughly the cube of the number of fundamental particles in the observable universe, so there is no known means for recording all of those combinations.

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UJJWAL BARMAN 2015-8-27

explain what to do with : .....having difficulty with this.......

Walter Roberson 2015-8-27

A = ABCD(:, 1); B = ABCD(:, 2);

etc. The 5th solution would be A(5),B(5),C(5),D(5)

You asked for all of the solutions and this is all of the solutions. Millions of them.

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Kelly Kearney 2015-8-27

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在 MATLAB Online 中打开

For just the integers:

 tmp = nchoosek(1:89,4);
 a = tmp(:,1);
 b = tmp(:,2);
 c = tmp(:,3);
 d = tmp(:,4);

The nchoosek function automatically sorts its results, so you don't have to worry about the inequality check. You could use the same function to test non-integers, too, though as everyone has pointed out the size of your arrays will quickly get out of control as you increase resolution.

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Roger Stafford 2015-9-4

Kelly's answer using 'nchoosek' is the best one, Ujjwal, and you should accept it. It will give you 89!/4!/85! = 2,441,626 possible combinations.

Note however that he misstates things a bit where he asserts that 'nchoosek' sorts the results. It does not. It actually uses the same order as was present in the received vector argument, which in the case of 1:89 would happen to be sorted.

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UJJWAL BARMAN 2015-9-4

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fourcombination.m

i am attaching a programming file that i have done which has runned sucessfully but i am having problem to save the output value of all the combination.please suggest how to save all the output data.