用Java实现两个矩阵的相乘
我试着将两个矩阵相乘。 我尝试使用R软件:检查此线程: 现在我尝试用Java做同样的事情 我使用Jama库来创建矩阵 我的幂函数用Java实现两个矩阵的相乘,java,r,matrix,jama,Java,R,Matrix,Jama,我试着将两个矩阵相乘。 我尝试使用R软件:检查此线程: 现在我尝试用Java做同样的事情 我使用Jama库来创建矩阵 我的幂函数 public Matrix power(Matrix M, double p) { EigenvalueDecomposition evd = M.eig(); Matrix D = evd.getD(); for (int i = 0; i < D.getColumnDimension(); i++) { D.set(i
public Matrix power(Matrix M, double p) {
EigenvalueDecomposition evd = M.eig();
Matrix D = evd.getD();
for (int i = 0; i < D.getColumnDimension(); i++) {
D.set(i, i, Math.pow(D.get(i, i), p));
}
Matrix V = evd.getV();
return V.times(D.times(V.transpose()));
}
double[][] matDouble1 = {{0.25, 0.25, 0.25, 0.25}};
double[][] matDouble2 = {{0, 0, 1, 0},
{0.333, 0, 0.333, 0.333},
{1, 0, 0, 0},
{0, 1, 0, 0}};
Matrix mat1 = new Matrix(matDouble1);
Matrix mat2 = new Matrix(matDouble2);
mat2 = power(mat2, 10000);
mat1 = mat1.times(mat2.transpose());
而不是
0.5 0 0.5 0
有了R我就知道了
mpower = function(M,p) {
A = as.matrix(M)
if (dim(A)[1] != dim(A)[2]) stop("not a square matrix")
# M^{-1} = the matrix inverse of M
if (p==-1) return(solve(A))
# M^0 = I
if (p==0) return(diag(1,dim(A)[1],dim(A)[2]))
# M^1 = M
if (p==1) return(A)
if (p < -1) stop("only powers >= -1 allowed")
if (p != as.integer(p)) stop("only integer powers allowed")
R = A
for (i in 2:p) {
R = R %*% A
}
return(R)
在MATLAB中做了如下操作:
>> a = [0.25, 0.25, 0.25, 0.25]
a =
0.2500 0.2500 0.2500 0.2500
>> b= [0 0 1 0; .333 0 .333 .333; 1 0 0 0; 0 1 0 0]
b =
0 0 1.0000 0
0.3330 0 0.3330 0.3330
1.0000 0 0 0
0 1.0000 0 0
>> c = b^10000
c =
1.0000 0 0 0
0.4993 0 0.4993 0
0 0 1.0000 0
0.4993 0 0.4993 0
>> a*c'
ans =
0.2500 0.2496 0.2500 0.2496
Java代码工作正常。然而:
>> a*c
ans =
0.4996 0 0.4996 0
因此,矩阵在R代码中被转置,因为在as.matrix
语句中需要byrow=TRUE
澄清:
mat2<-matrix(c(0,0,1,0,0.3,0,0.3,0.3,1,0,0,0,0,1,0,0),nrow=4)
你想要
mat2<-matrix(c(0,0,1,0,0.3,0,0.3,0.3,1,0,0,0,0,1,0,0),nrow=4,byrow=TRUE)
对于r,我得到:0.4996252 0.4996252 0或者你不应该在Java代码中转置矩阵,如果你想要这个等式的话。相同吗?你是在告诉我mat2最终是对称的吗?在这一页上:你可以看到结果:我只是搜索一种方法来获得相同的值,然后在R中(不带byrow=TRUE),你应该从
mat1.times(mat2)
中获得。如果您打印mat2
,可能有助于了解发生了什么。
>> a*c
ans =
0.4996 0 0.4996 0
mat2<-matrix(c(0,0,1,0,0.3,0,0.3,0.3,1,0,0,0,0,1,0,0),nrow=4)
0 0.3 1 0
0 0 0 1
1 0.3 0 0
0 0.3 0 0
mat2<-matrix(c(0,0,1,0,0.3,0,0.3,0.3,1,0,0,0,0,1,0,0),nrow=4,byrow=TRUE)
0 0 1 0
0.3 0 0.3 0.3
1 0 0 0
0 1 0 0