Inquiry about ceil function.

Question

Angel Lozada 2023-6-19

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1985409-inquiry-about-ceil-function

编辑： Stephen23 2023-6-19

采纳的回答： Stephen23

在 MATLAB Online 中打开

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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Answer 1

Stephen23 2023-6-19

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https://ww2.mathworks.cn/matlabcentral/answers/1985409-inquiry-about-ceil-function#answer_1258944

编辑：Stephen23 2023-6-19

在 MATLAB Online 中打开

"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