Extract element from column vector with condition

I have column vector

P=[ 0; 212; 111; 190; 0; 223; 123; 200; 189; 219; 0; 190; 175; 202; 167; 181

....and so on]

I want to extract the 2nd and 3rd elements from the left 0 element IF LENGTH BETWEEN TWO 0 (the left 0 and right 0) is GREATER THAN 3. Save 2nd position elements in P2 column vector and 3rd position elements in P3 column vector. The result should be

After extraction, the remaining elements should be placed into P1 such as

P1 = [ 0; 212; 111; 190; 0; 223; 189; 219; 0; 190; 167; 181 ....and so on]

P2 = [123; 175]
P3 = [200; 202]

[Azzi Abdelmalek]

There is no P2 in your result, what is P0? Can you remove the symbols *?

[Sagar Dhage]

HI Azzi, I edited the question

[Azzi Abdelmalek]

How did you get P1?

[Sagar Dhage]

by removing extracted element 2nd position and 3rd position from 0

[Azzi Abdelmalek]

This is not clear, what about 212 and 111 the second and the third element of P?

[Sagar Dhage]

Oh sorry, extract 2nd and 3rd position element if IF LENGTH BETWEEN two 0 is GREATER THAN 3.

[Image Analyst]

It might be clearer if you said "is 4 or more" rather than is "greater than 3". So the left run has 121, 111, 190 and that's 3, but not more than 3 (not 4 or greater) so those are left alone and get transferred to P1.

It's fairly easy if you have the Image Processing Toolbox. Do you?

Answer 1

[Nir Rattner]

You can use the “find” function to find the indices of your zeros and then subtract each index by the one before to make sure the distance between them is not too large.

P=[ 0;  212; 111; 190; 0;  223; 123; 200; 189; 219; 0; 190; 175; 202; 167; 181; 0;];

Pzeros = find(P == 0);
violators = Pzeros(find(Pzeros(2 : end) - Pzeros(1: end - 1) > 4));

P1 = P;
P1([violators + 2; violators + 3]) = [];

P2 = P(violators + 2);
P3 = P(violators + 3);

[Sagar Dhage]

Thank Nir...

Answer 2

[Azzi Abdelmalek]

Edit

P=[ 0; 212; 111; 190; 0; 223; 123; 200; 189; 219; 0; 190; 175; 202; 167; 181 ]
ii=strfind(P'~=0,[0 1])
idx=ii([diff([ii numel(P)])]>4)
P1=P'
jj=[idx+2 idx+3]
P1(jj)=[]
P2=P(idx+2)'
P3=P(idx+3)'

[Sagar Dhage]

Thanks Azzi..its working..

Answer 3

[Image Analyst]

Method using the Image Processing Toolbox:

P=[ 0; 212; 111; 190; 0; 223; 123; 200; 189; 219; 0; 190; 175; 202; 167; 181]
P2 = [];
P3 = [];
measurements = regionprops(P~=0, P, 'PixelValues', 'Area')
for k = 1 : length(measurements)
  % Show length of this stretch in the command window:
  fprintf('Area of stretch #%d = %d\n', k, measurements(k).Area);
  % Tack onto P2 and P3 if the length >= 4.
  if measurements(k).Area >= 4
    P2 = [P2, measurements(k).PixelValues(2)];
    P3 = [P3, measurements(k).PixelValues(3)];
  end
end
% Show in command window:
P2
P3

[Sagar Dhage]

Hi.. here I am not getting P = [P=[ 0; 212; 111; 190; 0; 223; 123; 200; 0; 190; 167; 181] after removing P2 and P3..How get this modified P? Suppose P have corresponding vector also. How to find corresponding T2, T3 for P2 and P3? also If Area=3, its not considering elements in P1,P2,P3 vector..

[Image Analyst]

I'm leaving on a week long trip in an hour. It looks like you've accepted an answer so then just go with that.

[Sagar Dhage]

I have modified your programme.. nw its gives wat I want..Thank you.

% measurementsX = regionprops(Px~=0, Px, 'PixelValues', 'Area') % for k = 1 : length(measurementsX)

for k = 1 : length(measurementsX) % Show length of this stretch in the command window: %fprintf('Area of stretch #%d = %d\n', k, measurementsX(k).Area); % Tack onto P2 and P3 if the length >= 4. if measurementsX(k).Area == 1 P1X_1 = [P1X_1, measurementsX(k).PixelValues(1)]; end end

for k = 1 : length(measurementsX) % Show length of this stretch in the command window: %fprintf('Area of stretch #%d = %d\n', k, measurementsX(k).Area); % Tack onto P2 and P3 if the length >= 4. if measurementsX(k).Area == 3 P1X_3 = [P1X_3, measurementsX(k).PixelValues(1)]; P2X_3 = [P2X_3, measurementsX(k).PixelValues(2)]; P3X_3 = [P3X_3, measurementsX(k).PixelValues(3)]; end end

for k = 1 : length(measurementsX) % Show length of this stretch in the command window: %fprintf('Area of stretch #%d = %d\n', k, measurementsX(k).Area); % Tack onto P2 and P3 if the length >= 4. if measurementsX(k).Area ==5 P1X_5 = [P1X_5, measurementsX(k).PixelValues(1)]; P4X_5 = [P4X_5, measurementsX(k).PixelValues(2)]; P5X_5 = [P5X_5, measurementsX(k).PixelValues(3)]; P2X_5 = [P2X_5, measurementsX(k).PixelValues(4)]; P3X_5 = [P3X_5, measurementsX(k).PixelValues(5)]; end end