<p>The documentation says &quot;rms variance&quot;, which means <span class="math-container">$\sigma$</span> and not <span class="math-container">$\sigma^2$</span>. (&quot;rms&quot; is short for &quot;root mean square&quot;.) I can't attest that the code returns the correct thing, but the documentation at least is clear to me.</p>

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2024-07-24T15:30:44.813Z
2024-07-24T18:23:48.747Z
2024-07-24T18:23:48.747Z
Sten
<p>Can anyone tell me if the <a href="https://bdiemer.bitbucket.io/colossus/cosmology_cosmology.html#cosmology.cosmology.Cosmology.sigma" rel="nofollow noreferrer">Colossus cosmology.sigma()</a> function returns variance, which is sigma^2, or sigma and I have to square it to get variance?  All of the documentation regarding this is completely ambiguous and I cannot find an answer.  I want to pass the return value to EPS calculation function and don't know if I need to square it first.  In the <a href="https://bdiemer.bitbucket.io/colossus/cosmology_cosmology.html" rel="nofollow noreferrer">Colossus documentation</a>, the function is called &quot;sigma&quot; but the verbiage says it is &quot;variance&quot;.  Which is it?  Please help.</p>

<galaxy>
What does Colossus cosmology.sigma() return
Bill Robinson
# What does Colossus cosmology.sigma() return

(Asked by: username_0 on 2024-07-22)

Can anyone tell me if the [Colossus cosmology.sigma()](https://bdiemer.bitbucket.io/colossus/cosmology_cosmology.html#cosmology.cosmology.Cosmology.sigma) function returns variance, which is sigma^2, or sigma and I have to square it to get variance? All of the documentation regarding this is completely ambiguous and I cannot find an answer. I want to pass the return value to EPS calculation function and don't know if I need to square it first. In the [Colossus documentation](https://bdiemer.bitbucket.io/colossus/cosmology_cosmology.html), the function is called "sigma" but the verbiage says it is "variance". Which is it? Please help.

**Tags:** galaxy


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## 1 answers

### Answer by username_1 on 2024-07-24. Score: 1

The documentation says "rms variance", which means $\sigma$ and not $\sigma^2$. ("rms" is short for "root mean square".) I can't attest that the code returns the correct thing, but the documentation at least is clear to me.


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