How to resolve the error of looping

Dear All,

I wrote some script looping to determine the thresh value for certain volume (26.67). But I got error like below. The set imageas data set as attached.

Can help me?

%% I131 10:1 graycutoff 100000 latest GUNA FWHM
clc
clear all
close all
[spect map]=dicomread('I-131sphere10nisbah1.dcm');
info = dicominfo('I-131sphere10nisbah1.dcm');
%gp=info.SliceThickness;
spect=(squeeze(spect));%smooth3
aa=size(spect);aa=aa(3);
imshow3D(spect)
figure, imtool3D(spect)

seedR1 = 58; seedC1 = 76; seedP1 = 45;

W = graydiffweight(spect, seedC1, seedR1, seedP1, 'GrayDifferenceCutoff', 1000000000);

for thresh =0.0001:0.0001:0.9999;
    [BW, D] = imsegfmm (W, seedC1, seedR1, seedP1, thresh);
    T = regionprops ('table', BW,'Area','Centroid');	
    if T(1)==26.67; %want to know thresh value for volume 26.67
        gray_weight = thresh;
        volume = T(1)
        break
    end
end

Error using ()

Subscripting into a table using one subscript (as in t(i)) is not supported. Specify a row

subscript and a variable subscript, as in t(rows,vars). To select variables, use t(:,i) or for

one variable t.(i). To select rows, use t(i,:).

Answer 1

[Image Analyst]

T is a table with the first column being the blob area and the second column being (x,y) of the centroid. Row 1 is for blob %1, row 2 is for blob #2, and so on. T(1) doesn't make sense because T, when using numerical indexes, is a 2-D array, not a 1-D array. So if you wanted the area of blob #2, you'd reference it with 2 indexes as T{2, 1} (with braces) or as T.Area(2) (equivalent but using the variable name of the column). I don't know how many blobs you will have in your binary image.

And you should not use regionprops for volumes, you should use the 3-D version regionprops3 to get volume of blobs.

Also you should not use fractional numbers for the area or volume since regionprops returns them as integer values (the discrete number of pixels or voxels), not as floating point areas or volumes. Even if it were, you should not compare floating point numbers with ==, you should use ismembertol. See the FAQ: https://matlab.fandom.com/wiki/FAQ#Why_is_0.3_-_0.2_-_0.1_(or_similar)_not_equal_to_zero?

[mohd akmal masud]

Dear @Image Analyst

seedR1 = 58; seedC1 = 76; seedP1 = 45;
W = graydiffweight(spect, seedC1, seedR1, seedP1, 'GrayDifferenceCutoff', 1000000000);

for thresh =0.0001:0.0001:0.9999;
     [BW, D] = imsegfmm (W, seedC1, seedR1, seedP1, thresh);
     T = regionprops('table', BW,'Area','Centroid');	
     if T{2,1}==26.67;
           gray_weight = thresh
           volume = T{2,1}
           break
      end
end

Error using {}

Row index exceeds table dimensions.

[Walter Roberson]

regionprops found either no blobs or one blob, so row 2 of the table does not exist.

Do not use == to compare floating point numbers. == between two values of the same data type looks for bit-for-bit being exactly the same (with the exception that +0 and -0 are treated as equal.) It is extremely improbable that you will get a blob with area exactly

fprintf('%.999g\n', 26.67)

26.6700000000000017053025658242404460906982421875

You would be much more likely to get a blob whose area was 26 + 2/3 to within rounding error.

See ismembertol

[mohd akmal masud]

Dear @Walter Roberson,

can you write the script for me. I cannot understand.

[mohd akmal masud]

Dear @Image Analyst and @Walter Roberson,

Actually, my original script is like below:

seedR1 = 58; seedC1 = 76; seedP1 = 45;
W = graydiffweight(spect, seedC1, seedR1, seedP1, 'GrayDifferenceCutoff', 1000000000);
thresh =0.0001;
[BW, D] = imsegfmm (W, seedC1, seedR1, seedP1, thresh);
T = regionprops('table', BW,'Area','Centroid')


    Area             Centroid         
    ____    __________________________

     12     75.833    58.167      44.5

Then I have to change the thresh (try and error) until I got the Area is 267.

But I want to do something like looping or iteration, which is I set the Area is 267. Then wrote the script like below:

seedR1 = 58; seedC1 = 76; seedP1 = 45;

     W = graydiffweight(spect, seedC1, seedR1, seedP1, 'GrayDifferenceCutoff', 1000000000);
     for thresh =0.0001:0.0001:0.9999
         [BW, D] = imsegfmm (W, seedC1, seedR1, seedP1, thresh);
          T = regionprops('table', BW,'Area','Centroid');	
         if T{1,1}==267
             gray_weight = thresh;
             volume = T{1,1};
         end
     end
     
     

Can you help me @Image Analyst @Walter Roberson?

[Walter Roberson]

you posted this as s new question and I answered there

[Peter Perkins]

You might find T.Area(1), or even T{1,"Area"}, easier to read than T{1,1}.