I have an array of data [ 1.1 0.5 1.8 2.5 0.6 2.0 2.1 4.0 1.3 1.4 5.0 4.2 2.2 3.2 3.4 3.5 3.3 4.8 1.11 2.0 2.5] I need a code pick data points incrementally from 1.1 until it get to the peak then start selecting after the peak in deceasing order.

I have an array of data [ 1.1 0.5 1.8 2.5 0.6 2.0 2.1 4.0 1.3 1.4 5.0 4.2 2.2 3.2 3.4 3.5 3.3 4.8 1.11 2.0 2.5] I need a code pick data points incrementally from 1.1 until it gets to the peak then start selecting after the peak in decreasing order. The expected outcome is [ 1.1 1.8 2.5 4.0 5.0 4.2 2.2 1.11] starting from the first element (1.1) the next element is 1.8 dropping 0.5 until getting to the peak (5.0) and then start decreasing from 5.0 to 1.11. the number of elements in the final output will reduce.

[KSSV]

How it is different from https://in.mathworks.com/matlabcentral/answers/351929-i-have-an-array-of-data-1-1-0-5-1-8-2-5-5-0-4-2-3-3-4-8-2-5-after-the-first-number-1-1-need-pi

[Olumide Omotere]

When I increase the number of elements in the array the code did not generate the expected outcome. for this, there are more elements in the array

Answer 1

[Stephen23]

V = [1.1 0.5,1.8,2.5,0.6,2.0,2.1,4.0,1.3,1.4,5.0,4.2,2.2,3.2,3.4,3.5,3.3,4.8,1.11,2.0,2.5];
[~,idx] = max(V);
N = V(1);
X = false(size(V));
for k = 1:idx
    X(k) = V(k)>=N;
    N = max(V(k),N);
end
for k = idx:numel(V)
    X(k) = V(k)<=N;
    N = min(V(k),N);
end
Z = V(X);

Generates this output vector:

>> Z
ans =
   1.1000   1.8000   2.5000   4.0000   5.0000   4.2000   2.2000   1.1100

Compared to the requested output:

>> [ 1.1 1.8 2.5 4.0 5.0 4.2 2.2 1.11]
ans =
   1.1000   1.8000   2.5000   4.0000   5.0000   4.2000   2.2000   1.1100

[Olumide Omotere]

thank you

Answer 2

[Image Analyst]

1.8 is not an increment of 1.1 above 1.1, and 2.5 is not 1.1 above 1.8. And you can't add any number of 1.1's to 1.1 to get exactly 5. So I'm not sure what rule you're using but it's not [1.1, 2.2, 3.3, 4.4, 5.5, ...] etc.

Anyway, find the max, then use the colon operator:

   m = [ 1.1 0.5 1.8 2.5 0.6 2.0 2.1 4.0 1.3 1.4 5.0 4.2 2.2 3.2 3.4 3.5 3.3 4.8 1.11 2.0 2.5] 
   maxValue = max(m)
   % Create vector increasing from 1.1 to the max in steps of 1.1,
   % then going down from the max to 1.11 in steps of -0.5:
   m2 = [1.1 : 1.1 : maxValue, (maxValue - 0.5) : -0.5 : 1.11]

[Olumide Omotere]

Thank you image analyst for your response but the outcome is different.The expected outcome is [1.1 1.8 2.5 5.0 4.2 3.3 2.5]the code should pick data points monotonically increasing before the peak and monotonically decreasing after the peak