Function behaves unexpectedly on array inputs. To improve performance, properly vectorize your function to return an output with the same size and shape as the input arguments

Why am I getting the warning?

EDIT: removed VER information.

%% Hill equation

% Rate = Vmax * S^n / (K^n + S^n)

hill = @(S,Vmax,K,n) Vmax*S^n / (K^n + S^n);

%Check Michaelis Menton Function using S, Vmax=1, Km=0.1, and n=1)

hill_1 = @(S) hill(S, 1, 0.1, 1);

figure(1)
fplot(hill_1, [0,3])  

Warning: Function behaves unexpectedly on array inputs. To improve performance, properly vectorize your function to return an output with the same size and shape as the input arguments.

Answer 1

[Swastik Sarkar]

Hi @Elle,

While the formula is correct, the MATLAB code provided works well for scalar values but requires element-wise operations when working with matrices. By default, MATLAB assumes matrix operations on the variables. To address the warning encountered, the code should be modified as follows:

% Note element-wise operations
hill = @(S,Vmax,K,n) Vmax .* S.^n ./ (K.^n + S.^n);

% Check Michaelis-Menten Function using S, Vmax=1, Km=0.1, and n=1
hill_1 = @(S) hill(S, 1, 0.1, 1);

% Plot the function
figure(1)
fplot(hill_1, [0, 3])

Further information can be found in the following documentation::

https://www.mathworks.com/help/matlab/matlab_prog/array-vs-matrix-operations.html

Hope this helps.

[Elle]

Thank you! This was very helpful.

[Swastik Sarkar]

Hi @Elle,

I'm glad that this answer helped you! Please consider accepting the answer next time so that others in the community can benefit from it as well.

[Elle]

Done! Thanks