how can I generate a code based on specific value selection in a matrix?

9 次查看（过去 30 天）
JacobM
JacobM 2016-9-13
评论： JacobM 2016-9-14
I want to make a function that search for a value of y in x, either one element or sum of many elements, and return 1 or 0 to matrix Z, which is the same size as X, based on the elements chosen from X.
Example:
y=7;
x=[10 -1 -2 -3];
solution will be:
1) 10-1-2=7 ==> Z=[1 1 1 0];
2) 10-3=7 ==> Z=[1 0 0 1];
Any hints?

请先登录，再回答此问题。

采纳的回答

James Tursa
James Tursa 2016-9-13
编辑：James Tursa 2016-9-13
Here is one way as long as x is not too large. This technique will use too much memory if x is too large.
b = dec2bin(0:2^numel(x)-1)=='1'; % Intermediate step of producing all possible patterns
z = b(b*x'==y,:); % Pick off the rows of b that produce the desired sum
The rows of z contain the patterns that produce the desired sum.
  8 个评论
显示 6更早的评论
JacobM
JacobM 2016-9-14
This is maybe a follow-up question,
if z2 has 2's instead of 1's and I want them to appear in zout matrix, I did it like this:
z1=[1 0 0 1]; z2=[0 0 0 2; 0 0 2 0]; k = ~any(bsxfun(@and,z1,z2),2); zout = bsxfun(@xor,z1,z2(k,:)); % or as Andrei suggested
index=find(z2==2); % to find the index of 2's in z2 for i=1:length(index) j=index(i); zout(j)=zout(j)*2; % changing 1's to 2's in Zout based in position of 2's in z2 end
but did not work because of the size of zout, the index=6 7 while zout is 1*4 matrix, is there any other way?

请先登录，再进行评论。

更多回答（1 个）

John D'Errico
John D'Errico 2016-9-13
There may be millions, or millions or trillions of solutions, or only a few. Your problem is classically called an integer partition .
https://en.wikipedia.org/wiki/Partition_(number_theory)
For example, the number of distinct ways the number 1000 can be written as the sum of elements from the set [1:1000] is 24061467864032622473692149727991. A BIG number.
You can download my partitions tool from the file exchange, which can generate the entire set (where that is feasible given some rational amount of time and memory.) It allows you to specify the elements to be allowed in the sum.
https://www.mathworks.com/matlabcentral/fileexchange/12009-partitions-of-an-integer

类别

在 Help Center 和 File Exchange 中查找有关 Matrices and Arrays 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by