How do I fill a matrix with values using the tril, diag function without it overwritting the previous command?
19 visualizzazioni (ultimi 30 giorni)
Mostra commenti meno recenti
Hello. I am trying to do the following in a matrix. Please see attached. The code that I came up with keeps overwriting the previous code for the A matrix.
%Makes a 121 by 121 matrix of zeros
A=zeros(121);
%This makes a 121 by 121 matrix of ones
B = ones(121);
%This is element by element multiplication
matrix_I=-I.*B;
%This is the row vector for to get the ones in the 'A' matrix
V=ones(1,120);
%This makes the diagonal of ones in the 'A' matrix
A = diag(V,1);
A= tril(matrix_I);
A(120, 121) = -1;
%This is for all the -1 being multiplied by M
%for the given equation in book P3.4a but I solved it and set it equal to 0
A(:,121)=-1;
Please I need some help. Thank you.
2 Commenti
madhan ravi
il 1 Ago 2018
You want the lower diagonal of the matrix as -1 and the rest to be zeros ?
Risposta accettata
Rik
il 2 Ago 2018
Modificato: Rik
il 3 Ago 2018
You're close, see if the code below works for you.
I fixed some typos in the previous code. Now it runs and should give you the output you want.
num_el=121;I=1/3;
D=ones(num_el-1);%it's easier to skip the first column and last row first
A=tril(-I.*D);
A(1:(size(A,2)+1):end)=1;
A=[ones(num_el-1,1)*-I A;ones(1,num_el-1)*-I -1];
A(:,end)=-1;
2 Commenti
Rik
il 5 Ago 2018
Did this suggestion solve your problem? If so, please consider marking it as accepted answer. It will make it easier for other people with the same question to find an answer. If this didn't solve your question, please comment with what problems you are still having.
Più risposte (0)
Vedere anche
Categorie
Scopri di più su Operating on Diagonal Matrices in Help Center e File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!