Matrix is singular to working precision

When i run the below command the error is happen.

How should i do? i checked all things is oK but i dont know why the error occurs

%Computing heat flow in the bathroom floor

Edof=[1 1 2;

2 2 3;

3 3 4;

4 4 5;

5 5 6;

6 7 8;

7 9 10;

8 6 11;

9 11 12];

K=zeros(12);f=zeros(12,1);

f(3)=-30; f(4)=30;

ep1=[25];ep2=[250];ep3=[50];ep4=[6.66];ep5=[0.5];

ep6=[31.11];ep7=[6.25];ep8=[10.63];ep9=[7.7];

Ke1=spring1e(ep1);

Ke2=spring1e(ep2);

Ke3=spring1e(ep3);

Ke4=spring1e(ep4);

Ke5=spring1e(ep5);

Ke6=spring1e(ep6);

Ke7=spring1e(ep7);

Ke8=spring1e(ep8);

Ke9=spring1e(ep9);

K=assem(Edof(1,:),K,Ke1);

K=assem(Edof(2,:),K,Ke2);

K=assem(Edof(3,:),K,Ke3);

K=assem(Edof(4,:),K,Ke4);

K=assem(Edof(5,:),K,Ke5);

K=assem(Edof(6,:),K,Ke6);

K=assem(Edof(7,:),K,Ke7);

K=assem(Edof(8,:),K,Ke8);

K=assem(Edof(9,:),K,Ke9);

The temperature is prescribed in both

%air outside and air inside section of the floor which the temperatures are 22c

%and 5c respectively.The degree of freedom a1 and a12.

bc=[1 22;12 5];

%To solve the system for computing the temperature values T in the node points (given in (a)) and the boundary flows vector (r)we use function

%solveq.

[a,r]=solveq(K,f,bc);

Warning: Matrix is singular to working precision.

> In solveq (line 37)

In X9 (line 54)

%We use function extract to compute the temperatures of each element.

ed1=extract(Edof(1,:),a);

ed2=extract(Edof(2,:),a);

ed3=extract(Edof(3,:),a);

ed4=extract(Edof(4,:),a);

ed5=extract(Edof(5,:),a);

ed6=extract(Edof(6,:),a);

ed7=extract(Edof(7,:),a);

ed8=extract(Edof(8,:),a);

ed9=extract(Edof(9,:),a);

%The heat flow through each element is computed by using functions spring1s.

q1=spring1s(ep1,ed1);

q2=spring1s(ep2,ed2);

q3=spring1s(ep3,ed3);

q4=spring1s(ep4,ed4);

q5=spring1s(ep5,ed5);

q6=spring1s(ep6,ed6);

q7=spring1s(ep7,ed7);

q8=spring1s(ep8,ed8);

q9=spring1s(ep9,ed9);

Answer 1

[Alan Moses]

The warning “Matrix is singular to working precision” occurs if the matrix for which you are using to solve the system of linear equations is a singular matrix.

From your MATLAB script, line 37, which involves the solveq function has an input ‘K’ which is a singular matrix. Since the determinant of this matrix is zero, division by zero leads to computations with Inf and/or NaN, making the computed result unreliable. You can refer the same in this documentation under the “Examples” section.