Inquiry about ceil function.

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Angel Lozada
Angel Lozada 2023-6-19
编辑： Stephen23 2023-6-19
Hello.
I will really be appreciated if someone could help me with the follow line code (part of it).
I understand what ceil function does, however I do not understand why is necessary to sum + 1E-12
I have been looking in Matlab community, but I did not find an answer to this inquiry.
Also, I will really appreciate the link to read about this specific topic.
Regards.
clear;
data = readmatrix('Data 2');
t = seconds(data(:,1));
ixv = ceil(data(:,1) + 1E-12);
secv = accumarray(ixv, (1:size(data,1)).', [], @(x){data(x,[2 3])});
A2 = reshape(cell2mat(secv).', 2,10,[]);
tv = unique(ixv);
figure

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Stephen23
Stephen23 2023-6-19
编辑：Stephen23 2023-6-19
Ran in:
"I understand what ceil function does, however I do not understand why is necessary to sum + 1E-12"
In lieu of useful code comments explaining that magic number, my guess is that it is an attempt to account for some range of binary floating point errors in the input values. Compare:
ceil(10*(0:0.1:1))
ans = 1×11
0 1 2 4 4 5 6 7 8 9 10
ceil(10*(0:0.1:1)+1e-12)
ans = 1×11
1 2 3 4 5 6 7 8 9 10 11

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