利用Matlab进行交集、并集等运算

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~ Matlab是强大的数值分析与计算的软件,本例分享使用Matlab进行两个数集的交集、并集等运算。
intersect函数取交集
帮助文档: intersect Set intersection. C = intersect(A,B) for vectors A and B, returns the values common to the two vectors with no repetitions. C will be sorted. C = intersect(A,B,'rows') for matrices A and B with the same number of columns, returns the rows common to the two matrices. The rows of the matrix C will be in sorted order. [C,IA,IB] = intersect(A,B) also returns index vectors IA and IB such that C = A(IA) and C = B(IB). If there are repeated common values in A or B then the index of the last occurrence of each repeated value is returned. [C,IA,IB] = intersect(A,B,'rows') also returns index vectors IA and IB such that C = A(IA,:) and C = B(IB,:). [C,IA,IB] = intersect(A,B,'stable') for arrays A and B, returns the values of C in the same order that they appear in A. [C,IA,IB] = intersect(A,B,'sorted') returns the values of C in sorted order. If A and B are row vectors, then C will be a row vector as well, otherwise C will be a column vector. IA and IB are column vectors. If there are repeated common values in A or B then the index of the first occurrence of each repeated value is returned. [C,IA,IB] = intersect(A,B,'rows','stable') returns the rows of C in the same order that they appear in A. [C,IA,IB] = intersect(A,B,'rows','sorted') returns the rows of C in sorted order. In a future release, the behavior of the following syntaxes will change including: - occurrence of indices in IA and IB will switch from last to first - orientation of vector C - IA and IB will always be column index vectors - tighter restrictions on combinations of classes In order to see what impact those changes will have on your code, use: [C,IA,IB] = intersect(A,B,'R2012a') [C,IA,IB] = intersect(A,B,'rows','R2012a') If the changes in behavior adversely affect your code, you may preserve the current behavior with: [C,IA,IB] = intersect(A,B,'legacy') [C,IA,IB] = intersect(A,B,'rows','legacy') Examples: a = [9 9 9 9 9 9 8 8 8 8 7 7 7 6 6 6 5 5 4 2 1] b = [1 1 1 3 3 3 3 3 4 4 4 4 4 10 10 10] [c1,ia1,ib1] = intersect(a,b) % returns c1 = [1 4], ia1 = [21 19], ib1 = [3 13] [c2,ia2,ib2] = intersect(a,b,'stable') % returns c2 = [4 1], ia2 = [19 21]', ib2 = [9 1]' c = intersect([1 NaN 2 3],[3 4 NaN 1]) % NaNs compare as not equal, so this returns c = [1 3] Class support for inputs A and B, where A and B must be of the same class unless stated otherwise: - logical, char, all numeric classes (may combine with double arrays) - cell arrays of strings (may combine with char arrays) -- 'rows' option is not supported for cell arrays - objects with methods SORT (SORTROWS for the 'rows' option), EQ and NE -- including heterogeneous arrays derived from the same root class
简单示例:集合A: A = 1   2   3   4   5   6   7   8   9  10 集合B: B=5:2:15 B = 5   7   9  11  13  15
求A∩B为:intersect(A,B)

setdiff补集运算
setdiff Set difference. C = setdiff(A,B) for vectors A and B, returns the values in A that are not in B with no repetitions. C will be sorted. C = setdiff(A,B,'rows') for matrices A and B with the same number of columns, returns the rows from A that are not in B. The rows of the matrix C will be in sorted order. [C,IA] = setdiff(A,B) also returns an index vector IA such that C = A(IA). If there are repeated values in A that are not in B, then the index of the last occurrence of each repeated value is returned. [C,IA] = setdiff(A,B,'rows') also returns an index vector IA such that C = A(IA,:). [C,IA] = setdiff(A,B,'stable') for arrays A and B, returns the values of C in the order that they appear in A. [C,IA] = setdiff(A,B,'sorted') returns the values of C in sorted order. If A is a row vector, then C will be a row vector as well, otherwise C will be a column vector. IA is a column vector. If there are repeated values in A that are not in B, then the index of the first occurrence of each repeated value is returned. [C,IA] = setdiff(A,B,'rows','stable') returns the rows of C in the same order that they appear in A. [C,IA] = setdiff(A,B,'rows','sorted') returns the rows of C in sorted order. In a future release, the behavior of the following syntaxes will change including: - occurrence of indices in IA will switch from last to first - orientation of vector C - IA will always be a column index vector - tighter restrictions on combinations of classes In order to see what impact those changes will have on your code, use: [C,IA] = setdiff(A,B,'R2012a') [C,IA] = setdiff(A,B,'rows','R2012a')
例如,求上例中在集合A中,不在集合B中的元素。命令为setdiff(A,B)

setxor去两个集合交集的补集
例如setxor(A,B)= setxor(A,B) ans = 1   2   3   4   6   8  10  11  13  15
union取两者的并集
union(A,B)= union(A,B) ans = 1   2   3   4   5   6   7   8   9  10  11  13  15


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修水县17198062042: 用matlab求一个矩阵各行之间的交集 -
住江复方: 方法1 n=input('n=') z1=intersect(intersect(intersect(M1(n,:),M2(n,:)),M3(n,:)),M4(n,:)); z1=z1(z1~=0) 分别插入行值,就可以求出.方法2 for i=1:7; z=intersect(intersect(intersect(M1(i,:),M2(i,:)),M3(i,:)),M4(i,:)); z=z(z~=0) end

修水县17198062042: 请问在MATLAB中能求解集合的交集和并集吗
住江复方: 交集 intersect(A,B) 并集 union(A,B)

修水县17198062042: matlab怎么样求交集呀???? -
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修水县17198062042: matlab中如何求两个矩阵的交集 -
住江复方: >> help intersectINTERSECT Set intersection.INTERSECT(A,B) for vectors A and B, returns the values common to thetwo vectors. MATLAB sorts the results. A and B can be cell arrays ofstrings. INTERSECT(A,B,'rows') for matrices A and B ...

修水县17198062042: 如何用MATLAB取两集合的交集 -
住江复方: c = intersect(A, B) 返回A与B的交集. 例如: >> A = [1,3,5];B = 1:6; >> c = intersect(A, B) c = 1 3 5

修水县17198062042: 请问想用MATLAB求多个集合的交集,程序该怎么编??? -
住江复方: a1=[1,2,3,4,5,6];b1=[4,5,6,7,8,9];a2=[5,6,7,8,9,10];b2=[1,2,7,8,9,10];c11=intersect(a1,b1)c12=intersect(a1,b2)c21=intersect(a2,b1)c22=intersect(a2,b2)

修水县17198062042: matlab 如何求多个矩阵对应行的交集 -
住江复方: >> help intersect intersect set intersection. intersect(a,b) for vectors a and b, returns the values common to the two vectors. matlab sorts the results. a and b can be cell arrays of strings. intersect(a,b,'rows') for matrices a and b that have the same ...

修水县17198062042: Matlab数组怎么交集 -
住江复方: A = [7 1 7 7 4]; B = [7 0 4 4 0]; [C,ia,ib] = intersect(A,B)C = 4 7 ia = 5 4 ib = 4 1

修水县17198062042: 如何用matlab程序进行运算? -
住江复方: 表示方法有三种:(1)使用^运算符 ^,表示矩阵的乘方,例如:A^3.^,表示向量的乘方,例如:a.^3 其中“A”为矩阵;“a”为向量;“.”为点运算,表示对应元素进行运算.详见:matlab运算符 (2)使用power函数 power()函数,是matlab的乘方函数,例如:power(a,3),第一个参数为底,第二个参数为指数.其中“a”为向量;详见:help power doc power (3)使用乘积 a的立方,可表示为a.*a.*a.*a

修水县17198062042: 请问想用MATLAB求多个集合的交集,程序该怎么编??? -
住江复方: 你想把索引写进名字嘛,用eval函数.

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