Conditional statements on array.

Hello MathWorks community!

Could someone give me a hand?

I'm struggling on a loop involving a conditional statement in order to get a particular array.

This is my Input array (1x24):

Input = [0,0,0,0,0,5,6,7,25,68,0,0,0,0,0,36,221,78,14,16,96,75,0,0]

What I'm trying to check is if there is any value bigger than 100 on a 12 range positions of the array. In case the statement is true, I would like to make the 12 range values equal 1, otherwise equal 0. (Note: the array input dimensions will always be a multiple of 12)

The Output on this particular example should look like this:

Output = [0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,1,1,1,1,1,1,1,1,1]

The first 12 positions are equal to 0 because there aren't any values bigger than 100. But from 13 to 24 postions are equal to 1, because 221 is bigger than 100.

I hope I've explained my-self well enough.

Thanks for the help!

Answer 1

[Cris LaPierre]

This looks like a job for cummax, along with a logical array (ch 12 MATLAB Onramp).

Input = [0,0,0,0,0,5,6,7,25,68,0,0,0,0,0,36,221,78,14,16,96,75,0,0];
B = cummax(Input);
Output = B >= 100

Output = 1x24 logical array
   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   1   1   1   1   1   1   1   1

[Cris LaPierre]

I was too quick and didn't catch the intervals of 12.

Assuming your vector length is always a multiple of 12, it doesn't get too much more complicated.

Input = [0,0,0,0,0,5,6,7,25,68,0,0,0,0,0,36,221,78,14,16,96,75,0,0];
% Convert to a matrix with 12 rows, n columns
B2 = reshape(Input,12,[]);
% Determine the value of each column
BM = max(B2)>100

BM = 1x2 logical array
   0   1

% create new matrix of 0s and 1s
BM = BM.*ones(size(B2));
% Reshape back to a vector
Output = reshape(BM,1,[])

output = 1×24

0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1

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[Santos García Rosado]

Great! I was trying to find a way using the cummax documentation you provided. Your code works great anyway. Thank you so much Cris!

Answer 2

[David Hill]

i=reshape(Input,12,[])'>100;
Output=zeros(size(i));
for k=1:size(i,1)
    if nnz(i(k,:))>0
        Output(k,:)=1;
    end
end
Output=Output';
Output=Output(:)';

[Santos García Rosado]

Thank you for your help David. This works aswell.

Answer 3

[Mathieu NOE]

hello Santos

this is one way to do it

split the input vector in 12 long extracts, then search for any value inside that is above your threshold and do some outputs (0 or 1's vectors)

not the fanciest code but it works

Input = [0,0,0,0,0,5,6,7,25,68,0,0,0,0,0,36,221,78,14,16,96,75,0,0];

ll = length(Input);
threshold = 100;
offset = 12;
loops = fix(ll/offset);
Output  = [];

for ci = 1:loops
    ind = 1+(ci-1)*offset;
    input_extract = Input(ind:ind+offset-1);
    if any(input_extract >= threshold)
        out = ones(1,offset);
    else
        out = zeros(1,offset);
    end
    
    Output  = [Output  out];
end

[Santos García Rosado]

You're right. Not the fanciest but still works. Thank you!