,我该怎么办
我想在MATLAB中创建一个稀疏矩阵,以计算第二个衍生物。目前,我以以下方式创建它:
r_num = 1000;
r_square_num = r_num*r_num;
A = sparse(-30*diag(ones(r_square_num,1),0)+16*diag(ones(r_square_num-r_num,1),r_num)+16*diag(ones(r_square_num-r_num,1),-r_num)-diag(ones(r_square_num-2*r_num,1),-2*r_num)-diag(ones(r_square_num-2*r_num,1),2*r_num));
但是,由于diag
和ones
创建密集的矩阵,这是不可能的,这会溢出我的内存。如果事先已经知道了次级和三元对角线的位置,那么我可以以以下方式重写:
A = spdiags([-1*ones_vec 16*ones_vec -30*ones_vec 16*ones_vec -1*ones_vec], -2:2, r_square_num, r_square_num);
但是,如果对角线之间的距离取决于r_num
?
第二个输入参数(d
(可以是任何向量,例如[-1:1]
,[-2,0,2]
或[-5,3]
。因此,以下内容应起作用:
A = spdiags([-1*ones_vec 16*ones_vec -30*ones_vec 16*ones_vec -1*ones_vec], (-2:2)*r_num, r_square_num, r_square_num);