Inverse matrix

M_det.m

function B=M_det(A) %Handwrited n*n matrix determinant function
[n,n1]=size(A);
if n~=n1
    fprintf('Error using det\nMatrix must be square.\n')
elseif n==1
    B=A;
elseif n==2
    B=det2(A);
else
    B=det3(A);
end
end

function B=det2(A)
B=A(1,1)*A(2,2)-A(1,2)*A(2,1);
end

function B=det3(A)
C=A;
[~,n]=size(A);
B=0;
for k=1:n
        C(1,:)=[];
        C(:,k)=[];                                                    %make submatrix
        if size(C)==2                                            %tell if C is a smallest submatrix
            if rem(k+1,2)==0                                %tell if 1+k is even
                B=B+A(1,k)*det2(C);
                C=A;
            else
                B=B-A(1,k)*det2(C);
                C=A;
           end
        else
            B=B+det3(C);                                       %recursive make submatrix and get det(C)
        end
end
end

M_inv.m

function B=M_inv(A)   %Handwrited n*n matrix inverse function
if M_det(A)==0
    fprintf('Warning: Matrix is close to singular or badly scaled. Results may be inaccurate.\n')
end
[n,~]=size(A);
B=zeros(n);
for i=1:n
    z=A;
    a=1;
    while a<=n               %set augmented matrix of x
        if a==i
            z(a,n+1)=1;
            a=a+1;
        else
            z(a,n+1)=0;
            a=a+1;
        end
    end
    for j=1:n-1                       % get up triangle matrix of x
        for k=j+1:n
            a=z(k,j)/z(j,j);
            z(k,:)=z(k,:)-z(j,:)*a;
        end
    end
    for j=n:-1:2                       %get diagonal matrix of x
        for k=j-1:-1:1
            a=z(k,j)/z(j,j);
            z(k,:)=z(k,:)-z(j,:)*a;
        end
    end
    for j=1:n                            
        B(j,i)=B(j,i)+z(j,n+1)/z(j,j);
    end
end
end