Sum of elements in an array over x

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Jacob Merriman
Jacob Merriman 2020-6-10
评论： Turlough Hughes 2020-6-10
Hello all,
I am looking to find the sum of elements in an array which exceed a certain value, e.g. 0.05.
I have this array: [0.023 0.056 0.053 0.034 0.021 0.075 0.088]
As you can see, 4 elements are over 0.05. However, I don't want to know 'how many elements' are over 0.05, I want to find the cumulative sum of the elements which match my criteria.
In this case: 0.056 + 0.053 + 0.075 + 0.088.
Total = 0.272
Can anyone help?
kind regards,
Jacob
  2 个评论
Jacob Merriman
Jacob Merriman 2020-6-10
编辑：Jacob Merriman 2020-6-10
Just to let people know, I found a way to solve this by simply deleting the elements in the array which were less than 0.05 and creating a new variable. Then we can simply sum the new variable.
Turlough Hughes
Turlough Hughes 2020-6-10
As a point of clarification, you are looking to add elements where each individual element exceeds a value of 0.05?

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采纳的回答

Turlough Hughes
Turlough Hughes 2020-6-10
编辑：Turlough Hughes 2020-6-10
a = [0.023 0.056 0.053 0.034 0.021 0.075 0.088];
result = sum(a(a>0.05))
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Turlough Hughes
Turlough Hughes 2020-6-10
No problem, you to. I added a follow up comment just to remove any ambiguity.
Turlough Hughes
Turlough Hughes 2020-6-10
I think the wording is a bit ambiguous and could be interpreted both ways.

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更多回答（1 个）

Image Analyst
Image Analyst 2020-6-10
In general, this will do it. You need to use combnk() to get all possible combinations of elements added together. Then check the sum of each combination:
v = [0.023 0.056 0.053 0.034 0.021 0.075 0.088]
threshold = 0.05;
counter1 = 1;
counter2 = 1;
rowSum = 0;
for k = 1 : length(v)
indexes = combnk(1 : length(v), k); % Get all combinations.
[rows, columns] = size(indexes);
rowSum = rowSum + rows;
for row = 1 : rows
% For this particular combination...
thisRow = indexes(row, :);
theSum(counter1) = sum(v(thisRow));
% See if this sum is more than the threshold
if theSum(counter1) > threshold
fprintf('These %d elements sum to more than %.2f\n ', length(thisRow), threshold);
fprintf('%.3f + ', v(thisRow(1 : end-1)));
fprintf('%.3f = %.3f\n', v(thisRow(end)), theSum(counter1));
counter2 = counter2 + 1;
end
counter1 = counter1 + 1;
end
end
histogram(theSum)
grid on;
caption = sprintf('Histogram of sums after %d combinations', rowSum);
title(caption, 'FontSize', 20);
xlabel('Sum', 'FontSize', 20);
ylabel('Count', 'FontSize', 20);
You'll see 124 (counter2) lines in the command window printing out the sums that are more than your threshold, like these:
These 6 elements sum to more than 0.05
0.023 + 0.056 + 0.034 + 0.021 + 0.075 + 0.088 = 0.297
These 6 elements sum to more than 0.05
0.023 + 0.053 + 0.034 + 0.021 + 0.075 + 0.088 = 0.294
These 6 elements sum to more than 0.05
0.056 + 0.053 + 0.034 + 0.021 + 0.075 + 0.088 = 0.327
These 7 elements sum to more than 0.05
0.023 + 0.056 + 0.053 + 0.034 + 0.021 + 0.075 + 0.088 = 0.350

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