Problem with diff operating on a row vector from regionprops

Hello, I have an image which consists of 4 spots that I apply regionprops to:

area_measurements = regionprops(BW2,I,{'Area','Perimeter','MajorAxisLength','MinorAxisLength','Orientation','Eccentricity'});

I want to remove any spots that are different to the others. e.g the top left spot

I decided to use Major and Minor as my metric.

allMajor=[area_measurements.MajorAxisLength]
allMinor=[area_measurements.MinorAxisLength]

allMajor =

        272.44        227.15        264.20        264.85


allMinor =

        197.26         81.16        185.93        205.54

And then combine them, so

MM=[allMajor.*allMinor]

MM =

      53742.57      18435.82      49121.64      54437.08

and then calc their differences to be able to remove the worst one. (I was thinking to remove the one with the largest difference and then take the mean)

      y=diff(MM)

But this gives me an error:

      Array indices must be positive integers or logical values.

I can't see why this is the case.

Answer 1

[Nicolas B.]

Hi Jason,

I tried the following code:

MM = [53742.57, 18435.82, 49121.64, 54437.08];
y  = diff(MM);

I get the following answer:

y =

   1.0e+04 *

   -3.5307    3.0686    0.5315
   

Are you sure that you don't have a variable or one of your functions that is named diff? It could be that you are shadowing the diff function.

[Jason]

AAhhh...yes I do, thanks for this

Jason