Extract elements of the array using any

                A=[ 83  7 32 61;
                    91 13 17 48; 
                   126  9 34 60; 
                   172 11 36 60; 
                   213 43 34 12 ; 
                   254 13 25 60; 
                   287 14 36 59;
                   366  1  3 70];

In this i want to find the difference between 2 rows of the 1st element.If the difference between any of the two row is less than or equal to 8 than the i want to remove the entire row whose 1st element is greater.

Example: In the above array A ,difference between the 91-83=8. Now here i want to remove entire row which contains 91.

I tried with the following code

Diff_Arr=diff(A); %to find the difference between the rows)
New_Arr_A = A(~any((Diff_Arr(:,1) <=8),2),:) % To get a new matrix extracting 91 %
Output:
      New_Arr_A =[91 13 17 48; 
                 126 9 34 60; 
                 172 11 36 60; 
                 213 43 34 12 ; 
                 254 13 25 60; 
                 287 14 36 59;
                 366 1 3 70];

But with this it is removing the entire row which contains 83.Instead i want to retain the row which contains 83 and remove entire row which contains 91. It would be great if you let me know how this is done.

Looking forward to hear from you at the earliest

Thanks

Pankaja

Answer 1

[Star Strider]

This seems to be reasonably robust, providing the elements in the first column are always increasing between rows:

dA1 = diff(A(:,1));                             % Calculate Differences In First Column
idx1 = find((dA1 <= 8));                        % Find Indices Of Differences <= 8
[A1max,idx2] = max(dA1(idx1:idx1+1));           % Find Max Between Adjacent Elements
A(idx2+idx1-1,:) = [];                          % Result

Answer 2

[dpb]

Problem is you need to keep the length of the logical vector the same as the original length; diff shortens it by one without compensation. One possible way (of many)--

>> A([false;diff(A(:,1))<=8],:)=[]
A =
  83     7    32    61
 126     9    34    60
 172    11    36    60
 213    43    34    12
 254    13    25    60
 287    14    36    59
 366     1     3    70
>>

If it's needed to keep A and make a new array w/o the given line the negate the test a and select instead of clearing the found row--

B=A(~[false;diff(A(:,1))<=8],:);

Answer 3

[Andrei Bobrov]

A = [83    32     7    61
    91    13    17    48
    95     9    34    60
   172    11    36    60
   213    43    34    12
   254    13    25    60
   260    14    36    59
   268     1     3    70];

out = A;
l0 = diff(out(:,1));
l1 = abs(l0) <= 8;
i0 = sign(l0).*l1;
ii = find(i0);
out(ii + (i0(ii)<0),:) = [];