Hough Circle detection - error ↑ Error: Function definition not supported in this context. Create functions in code file. Not sure how to fix this in the code

I created a code to detect circles with radius range 30 - 40 and it is not working, error message: ↑

Error: Function definition not supported in this context. Create functions in code file.

I am new at MATLAB and not sure how to resolve this.

function [C]=circle_detection(I,R)

% convert to grayscale:

I = rgb2gray(imread(I));

% generate the edge image

BW= edge (I, 'canny');% binary output

% Parameterization

theta_sample_frequency= 0.01; % Quantization step size

theta=(0:theta_sample_frequency:2*pi);% gradient angle in radians

num_thetas=numel (theta);

[x, y] = size (BW);% input image dimension

x0 = (1:x);

y0 = (1:y);

acc = zeros(x,y);% accumulator 1.e. hough space

r=R;

% Hough transform

for xi=1:x

for yj=1:y

if BW(xi,yj)==1 % this is edge point

for theta_id= 1:num_thetas

th=theta(theta_id);

a=round(xi-r*cos(th));

b=round(yj-r*sin(th));

if(a>0&&a<=x&&b>0&&b<=y)

acc(a,b) = acc(a,b)+1;

end

end

end

end

end

% Extract the parameters

[M, I]= max(acc (:)); %#ok<ASGLU> % detecting the maxima

[a, b] = ind2sub (size (acc), I); % Its courdinate in HT space

C=[y0(b), x0(a)]; % Centre of the circle

end

I am getting following error:

function [C]=circle_detection(I,R)

↑

Error: Function definition not supported in this context. Create functions in code file.

[DGM]

Two things:

1: Where are you writing this? Is this in a standalone file by itself? in another function file? In a script file?

2: What version are you using? IIRC, the ability to add local functions inside script files wasn't introduced until R2016b or so.