Index in position 1 exceeds array bounds

Hi, I am running the Circular Hough Transform code (from Matlab) with different image inputted. However there is an error popping out mentioned that "Index in position 1 exceeds array bounds". I don know what is the reason behind it. Please help me on this !

A = imread('circle.png');
imshow(A);
[centers, radii, metric] = imfindcircles(A,[15 30]);
centersStrong5 = centers(1:5,:); 
radiiStrong5 = radii(1:5);
metricStrong5 = metric(1:5);
viscircles(centersStrong5, radiiStrong5,'EdgeColor','b');

[Adam Danz]

What line is causing the error?

Sharing the error message is helpful but you should share the entire copy-pasted error message and indicate which line is causing the error.

"Index in position 1 exceeds array bounds" is quite informative. It means you're asking for values that don't exist. Here's an example:

a = [1 2 3 4 5]
a(6)  % But there is only 5 values!  Error!

[Teik Jin Lim]

Hi,

I think I pasted the whole error that pop out on my command window. Only "Index in position 1 exceeds array bounds" is shown which put me in a confuse situation.

But in this error, which line is represented as position 1 ?

Answer 1

[David Hill]

If imfindcircles finds less than 5 circles you are going to error.

A = imread('circle.png');
imshow(A);
[centers, radii, metric] = imfindcircles(A,[15 30]);
a=max(5,length(centers));
centersStrong5 = centers(1:a,:); 
radiiStrong5 = radii(1:a);
metricStrong5 = metric(1:a);
viscircles(centersStrong5, radiiStrong5,'EdgeColor','b');

[Teik Jin Lim]

Thanks for your prompt response.

Just to make it clear, if i would like to make the code know that any conditions below 5 circles detected are acceptable, which line changes should i make it ?

In another words, which line of this code is causing the issue that provides the condition that imfindcircles finds less than 5 circles will pop out the error.

[Walter Roberson]

a=max(5,length(centers));

Suppose that 3 centers are found, then max(5,3) is 5. If 27 centers were found, max(5,27) would be 27. Therefore your max() call will not return a value less than 5, and will return all of the length if there is more.

centersStrong5 = centers(1:a,:); 

and there you try to index at least 5 even if there were only 3.

If you want at most 5 but fewer if that is all there is, then use min() instead of max()

[David Hill]

Yes, my mistake. Should have said,

a=min(5,length(centers));

[Walter Roberson]

I keep getting caught myself in thinking that the operation "at least so-many" should be a min() operation, because you want a minimum of so-many.

[Teik Jin Lim]

Yea. You solve that issue for me.

But sadly, when I try it with other image it doens't seems like working even though there is no error. I changed the sensitivy and radius, but the output is the same. No circle detected.