How to Convert vector elements to zero for certain N length when its values gets negative?

I have a column vector F= (0; 0; 0; 0; 5; 7; 12; 11; 23; 32; 22; 10; 8; -6 0; -8; 1; 4; 8; -5; 0; 0; 0; 6; 8; 9; 13; 14; 12; 23; 34; 22; 16; 17; 4; -5 ; -6; 5; 7; 0; 0; 0)

I want to convert values of F when it gets negative (in this case -6 and -5) till N (lets N=8)

so result would be F= (0; 0; 0; 0; 5; 7; 12; 11; 23; 32; 22; 10; 8; 0; 0; 0; 0; 0; 0; 0; 0; 0; 0; 6; 8; 9; 13; 14; 12; 23; 34; 22; 16; 17; 4; 0; 0; 0; 0; 0; 0; 0) how to do this?

Answer 1

[Azzi Abdelmalek]

F(F<0 & F>=-8)=0

[Sagar Dhage]

sorry, i think i have not explain well. F= [0; 0; 0; 0; 5; 7; 12; 11; 23; 32; 22; 10; 8; -6; 0; -8; 1; 4; 8; -5; 0 ; 0; 0; 6; 8; 9; 13; 14; 12; 23; 34; 22; 16; 17; 4; -5 ; -6; 5; 7; 0; 0; 0 ]

I want values after -6 gets converted to 0 from -6 to next N=8 values(in bold font) and same for when and after -5 (in bold font) so result should be F= [0; 0; 0; 0; 5; 7; 12; 11; 23; 32; 22; 10; 8; 0; 0; 0; 0; 0; 0; 0; 0; 0; 0; 6; 8; 9; 13; 14; 12; 23; 34; 22; 16; 17; 4; 0; 0; 0; 0; 0; 0; 0 ]

[Azzi Abdelmalek]

F= [0; 0; 0; 0; 5; 7; 12; 11; 23; 32; 22; 10; 8; -6 ;0; -8; 1; 4; 8; -5; 0; 0; 0; 6; 8; 9; 13; 14; 12; 23; 34; 22; 16; 17; 4; -5 ; -6; 5; 7; 0; 0; 0]
idx=find(F<0,1)
n=numel(F);
while ~isempty(idx)
  F(idx:min(idx+7,n))=0;
  idx=find(F'<0,1);
end

[Sagar Dhage]

Thanks Azzi...its working

Answer 2

[Yu Jiang]

while  ~isempty(find(F<0))
  id1 = find(F<0,1);
  id2 = min(id1 + 7, length(F));
  F(id1:id2) = 0;
end

[Sagar Dhage]

i want that 0 from this value till next 8 values....

[Yu Jiang]

How about this?

while  ~isempty(find(F<0))
  id1 = find(F<0,1);
  id2 = min(id1 + 7, length(F));
  F(id1:id2) = 0;
end

Answer 3

[Roger Stafford]

I am not sure what you mean in your remark "till N (lets N=8)". Do you mean that a maximum of N successive negative values in F are to be converted to 0 with all the possible remaining negative values, if any, unaffected? If so, the example you should have used ought to have demonstrated that behavior. In any case, here is code that would accomplish such a task:

 F(find(F<0,N)) = 0;

[Sagar Dhage]

N is next 8 values from -6 and -5. I want to convert all positive and negative values to 0 for this N=8 length. that is all values in old should be zero. your formula converts only negative.

Answer 4

[Roger Stafford]

I think I understand you now. How about this:

 n = length(F);
 for k = 1:n
   if F(k) < 0
     F(k:min(k+N-1,n)) = 0;
   end
 end

[Sagar Dhage]

thanks Roger.. its working..