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chop doesn't chop very small numbers

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Alec Poulin
Alec Poulin 2018-10-1
编辑： Alec Poulin 2018-10-2

I have a small number, say 1e-14, and I want to chop it to three decimals. In this case, it should give 0. Yet:

>> chop(1e-14, 3)
ans =
   1.0000e-14

What is going on?

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Star Strider
Star Strider 2018-10-1
The only reference I can find on an InterWeb search is the Wolfram function Chop—Wolfram Language Documentation (link).
I cannot find any documentation for a function of that exact name in MATLAB in a similar search.
Alec Poulin
Alec Poulin 2018-10-2
编辑：Alec Poulin 2018-10-2
That is weird, I cannot remember where I learned about this function. Anyway, on my computer, the file chop.m is located in /usr/local/MATLAB/R2018a/toolbox/control/ctrlobsolete. But then, I just saw that there is the word "obsolete" in the directory name...

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采纳的回答

Steven Lord
Steven Lord 2018-10-1
I believe chop is an old function from Control System Toolbox. I recommend using round instead. The default behavior of round is to round to N decimals but you can also use it to round to N significant digits (which is what chop(X, N) does.)
>> x = 1e-14;
>> round(x, 3)
ans =
0
>> round(x, 3, 'significant')
ans =
1.0000e-14

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