Vectorization of a for loop

Hello,

I am trying to eliminate the loop and vectorise this piece of code. Any ideas?

for k = 1:(length(P)-2)
  if ((P(k+1)-P(k)>0)&&(P(k+2)-P(k+1)<0));
      B(k+1) = 1;
  end
end

Thanks

Answer 1

[Peter O]

     v = 1:length(P)-2;
     ix = find( ((P(v+1) - P(v)) > 0) & ((P(v+2) - P(v+1)) < 0) ) + 1;
     B2(ix) = 1;

[jpedro]

Hello Peter,

Thanks for your answer, but that code doesn't give the same results as the for above

Answer 2

[Guillaume]

Well, P(k+1)-P(k) can be obtained in a vectorised way with the diff function, so, assuming that by default B(k) is zero:

B = diff(P(1:end-1)) > 0 & diff(P(2:end)) < 0 %no need to preinitialise B

If by default, B(k) is something else:

B(diff(P(1:end-1)) > 0 & diff(P(2:end)) < 0) = 1; %B must be preinitialised