How to avoid a numerical problem in a for loop

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Eli Dim
Eli Dim 2015-7-16
回答： Star Strider 2015-7-16
I have two input files T and dispatch_seq. My code looks at T and sees how many rows of dispatch_seq should be taken. The result is stored in Output.
load T.mat
load dispatch_seq.mat
for j = 1:length(T)
ph1 = cumsum(cell2mat(dispatch_seq{j}(:,2)));
DecR1 = 10*rem(ph1,1);
for k = 1:length(ph1)
if DecR1(k) <= 0.1
ph1(k) = round(ph1(k));
end
end
j_1 = find(ph1>=T(j),1);
Output(j) = {dispatch_seq{j}(1:j_1,:)};
if ph1(j_1) > T(j)
Output{j}{end,2} = (Output{j}{end,2}-ph1(j_1)+T(j));
end
end
Everything works as expected with the exception of Output{28,1} and Output{77,1}. What happens there is the number in the corresponding row of the vector T equals exactly the sum of all rows of dispatch_seq, but the result I get in Output is []. How can I avoid this error?

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Star Strider
Star Strider 2015-7-16
I apologise for the delay. Life intrudes.
I discovered a problem. When I inserted this line as a trace of the arguments to the ‘j_1’ assignment, just below your ‘j_1’ assignment:
fprintf(1,'\nmax(ph1) = %23.15E, T(%d) = %23.15E, -> max(ph1)-T(%d) = %23.15E\n', max(ph1), j, T(j), j, max(ph1)-T(j))
the result was:
max(ph1) = 4.086999999999996E+03, T(28) = 4.087000000000000E+03, -> max(ph1)-T(28) = -3.637978807091713E-12
but the difference was zero or positive for all prior values of ‘ph1’ and ‘T(j)’. So for j=28, the find call returns an empty value for ‘j_1’. That results in the empty elements in your cell array.
Since you’re testing for ph1 >= T(j), one option might be to subsequently define j_1=length(ph1) if ‘j_1’ is empty, or to introduce a tolerance, or just round ‘ph1’ such as:
j_1 = find(round(ph1)>=T(j),1);
Since I’m not certain what your code is doing (so it may not be an appropriate solution), I offer that only as a suggestion.

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