Incorrect number or types of inputs or outputs for function perturb.

n = 100;
A = rand(n);
AInv = inv(A);

x = ones(n, 1);
b = A * x;

bTilde = perturb(b, 1e-10);

Incorrect number or types of inputs or outputs for function perturb.

xApp = A\b;
xTildeApp = A\bTilde;

disp('x minus xTilde')
xdiff = norm(xApp-xTildeApp)/norm(xApp);

disp('b minus bTilde')
bDiff = norm(b-bTilde)/norm(b);

disp('estimate')
normA = norm(A);
normAInv = norm(AInv);

estimate = normA*normAInv*bDiff

What's wrong with perturb function input?

Answer 1

[Poorna]

Hi Kel,

How did come to know of the "perturb" function that you used? As far as I know, there is no "perturb" function to perturb a matrix. However there are "perturb" functions within different toolboxes that accepts different kinds of inputs. Two of them are listed below:

https://www.mathworks.com/help/fusion/ref/inssensor.perturb.html

https://www.mathworks.com/help/aerotbx/ug/inssensor.perturb.html

For your use case, you could manually create a perturbation matrix and add it to the input to create a perturbed matrix.

Hope this Helps!