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I want to round the actual value of a variable to a certain precision point.





(rounding to .00001)

Is this possible?

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closed as off topic by Marvis, Davide Giraudo, draks ..., Micah, tomasz Dec 23 '12 at 15:03

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Voting to close this as off-topic. –  user17762 Dec 23 '12 at 10:53
Yes, this question belongs to Stackoverflow. –  Barnabas Szabolcs Dec 23 '12 at 10:54
why is this off topic? –  Vigrond Dec 23 '12 at 10:54
This question could have had both a programmatic solution or mathematical. It turns out the solution was mathematical. I was leaning toward wanting a mathematical solution (as my research didn't find a programmatic solution), so I posted it here. –  Vigrond Dec 23 '12 at 10:57
In the FAQ, the fifth bullet says "We welcome questions about... Software that mathematicians use." –  robjohn Dec 23 '12 at 12:03

1 Answer 1

up vote 2 down vote accepted

$$ \left[ 10^5 x \right] / 10^5 $$

The idea is that $10^5$ times the rounded value of $x$ is an integer, so we simply shift the problem over so that we can ask for the nearest integer, then shift back.

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why would you think this would work? (it doesn't) can you explain your answer? –  Vigrond Dec 23 '12 at 10:46
Worked for me: (grr I can't format the link correctly: you'll have to copy/paste) wolframalpha.com/input/?i=Round%28%200.333333333333333333%20*%2010%5E‌​5%29%20/%2010%5E5 –  Hurkyl Dec 23 '12 at 10:48
Sorry I guess I didn't understand the rounding syntax. Thanks, this works perfectly in octave. –  Vigrond Dec 23 '12 at 10:53
Ah sorry. The typical symbols in mathematics notation are $\lfloor x \rfloor$ for the floor function, $\lceil x \rceil$ for the ceiling function, and $[x]$ for the nearest integer function. –  Hurkyl Dec 23 '12 at 10:54
@Hurkyl: where all of these characters are available, I like to use $[x]$ for nearest integer. However, for those of us who were stuck previously on ASCII only usenet forums, [x] usually meant "floor of $x$", and sometimes we get confused about its intended usage on math.SE. –  robjohn Dec 23 '12 at 17:08

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