CODEWITHSUNDEEP
matlaboctave
Gaston
Gaston

Reputation: 994

Graph user-defined function

I am trying to graph this custom function, but I can't find how. Is it even possible? All examples are about known functions (like sin or exp(x)).

I get the following error: 

error: myfun: A(I,J,...) = X: dimensions mismatch
error: called from
    myfun at line 28 column 16
    grafica1 at line 54 column 2
>>

Code:

function ph = myfun(gamma)
...

  for i = 1:N
    ....
        A(i,i) = alfa*gamma+(gamma+1)*i+p*(N-i);
      elseif j == i-1
        A(i,j) = -i*(i-1);
      elseif j == i+1
        A(i,j) = -p*(N-i)*(i-1)*(i+1)/i;
    ...
    b(i) = gamma * i;
  end

  v = A\b;
  for i = 1:N
    ph = ph + nchoosek(N,i)*p^i*v(i)/((1+p)^N);
  end

endfunction

call:

y=myfun(gamma);
plot(gamma,y)

Upvotes: 0

Views: 62

Answers (1)

Mingjing Zhang
Mingjing Zhang

Reputation: 943

The problem with your function is that it not designed with vectorization in mind. Specifically, when the input gamma is a row vector, alfa*gamma+(gamma+1)*i+p*(N-i); must also be a vector. Of course it will fail if you assign its value to A(i, j), which is a scalar.

I think your best option at this point is to compute the y values one at a time. This requires the least amount of change to your existing codebase.

y = zeros(size(gamma))
for i = 1:length(gamma)
  y(i) = myfun(gamma(i));       
end
plot(gamma, y);

Upvotes: 1

Related Questions