Make a loop to find each first positive value after a negative value in an vector.

HI,

I have a vector with about 2000 positive and negative values. I want to make a loop that finds the first positive point/value after the negative values.

Once the loop has found that point, check if more than 75% of all values after that point are positive.

If yes, save that point into point_found. If not, continue the loop to search for the next positive value/point in the vector.

Once the loop has again found that point, check if from there on, more than 75% of all values after that point are positive.

If yes, save that point into point_found. If not, continue the loop to search for the next positive value/point in the vector. and so on and on until the point/value is found.

If there is no such point or value put into point_found=9999

[madhan ravi]

What have you done for your homework?

[Lois Slangen]

What do you mean?

[David K.]

They are implying that this looks like you took a homework problem and instead of doing it just asked it here. It is generally preferred that when asking a question you show what you have tried already.

[Lois Slangen]

this is what I have have so far, but it doesn't work at all.

for i=1:length(list)

if list (i) >= 0 && list (i-1)<=0

point (i) = i;

end

if mean(list(point_found:end) >= 0) >= 0.75

point_found = point(i);

end

end

[Lois Slangen]

list is the name of my vector

Answer 1

[Mario Chiappelli]

Try this out:

numbers = [1,2,3,-1,2,3,4,5,6,-7,-8,10,4,64,12,12,432,221,12];

num = length(numbers);
negativeCheck = 0;
for i = 1:num
    if negativeCheck == 1
        disp(calculatePercent(i,num,numbers));
        if numbers(i) > 0 && calculatePercent(i,num,numbers) >= .75
            pointOfInterest(i) = numbers(i);
            pointOfInterestIndex(i) = i;
            negativeCheck = 0;
        end
    end
    if numbers(i) < 0
        negativeCheck = 1;
    end
end
pointOfInterest = nonzeros(pointOfInterest');
pointOfInterestIndex = nonzeros(pointOfInterestIndex');

function percent = calculatePercent(minValue, maxValue, list)
    checkerList = double(maxValue-minValue);
    for i = minValue:maxValue
        if list(i) >= 0
            checkerList(i) = 1;
        else
            checkerList(i) = 0;
        end
    end
    percent = mean(checkerList);
end

I added a list that creates an index of which values are stored so you know their position from the original vector.