MATLAB: We uploaded pictures of washer, screws, nails, and nuts( silver, black, gold). I am in charge of size, I am trying to input a median for the seperate categories. How to go about doing that?? The median will help in fidning what’s greaterandsmal

size project

Would I use the BW function??

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What is the "BW" function?

The first thing you have to do is separate them from their backgrounds. After that you can threshold to get a binary image. You can then use regionprops() to examine various aspects such as the area or the major axis length.

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MATLAB: Median Frequency

If I understand correctly, you want to find the frequency below which you have 50 percent of the signal power. If that's the case, you can use spectrum object to calculate the periodogram and then use cumsum to get the cumulative power distribution. You then just need to find the frequency corresponding to the 50th percetile of the power distribution, using your parameters as an example,

h = spectrum.periodogram;
Hpsd = psd(h,s,'Fs',1000,'NFFT',2*nextpow2(length(s)));
Pdist = cumsum(Hpsd.Data);
Freq = Hpsd.Frequencies;
OverHalfIdx = find(Pdist>=Pdist(end)/2,1,'first');
UnderHalfIdx = find(Pdist<=Pdist(end)/2,1,'last');
MidFreq = (Freq(OverHalfIdx)+Freq(UnderHalfIdx))/2

HTH

MATLAB: Discarding certain centroids found using regionprops

What do you mean it computes the centroid parts in a black area? There's no way that it does that.

It's possible the centroid of a blob isn't in the blob. But it's definitely not calculating centroids for the background. If you think of a blob in the shape of "U", the centroid will not lie in on the U.

If you want to keep only centroids that occur in the area of a blob, that's easily possible.

EDIT Per comment/clarification:

I would just use bwareaopen on your logical image to remove small blobs.

I = bwareaopen(I,10); %all objects with fewer than 10px gone.

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MATLAB: Median Frequency

MATLAB: Discarding certain centroids found using regionprops

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