Script file that sums values and checks against another vector?

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Isaac Al-rai
Isaac Al-rai 2018-1-31
编辑： Jan 2018-1-31
Hello, I am trying to perform a script file that executes a sum and check loop. I need to write a script such that it reads the values in x and sums them until the sum value exceeds n, where n assumes one at a time the values contained in the array: n = [65 156 187 42]. Store all the calculated sums (for each n) in a single array A.
I tried entering the following but am not sure this is correct.
if true
% code
end
x=HW1Rand;
r=0;
n=[65 156 187 42];
for ii=1:length(x)
for jj=length(n)
r=r+ii;
if r>n
Solution=n(jj);
break
end
end
end
HW1Rand is a 1x20 random vector. I am not sure If this is actually checking each individual values of n and breaking at that point and I still need to store this in a single array A. Is there anything I can do to make this work better? Apologies if the syntax is messy.

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回答（1 个）

Jan
Jan 2018-1-31
编辑：Jan 2018-1-31
x = HW1Rand;
sumx = cumsum(x); % Calculate the sum once only
n = [65 156 187 42];
Solution = nan(1, length(n)); % Pre-allocate
for jj = 1:length(n)
index = find(sumx > n(jj), 1, 'first');
if ~isempty(index)
Solution(jj) = sumx(index);
end
end
It is cheaper to calculate the cumulative sum once only. Then you can use find() instead of using a loop. Solution is pre-allocated with NaNs, because it is possible, that no elemen of sumx is larger than the current element of n.

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