<p>For future reference, I believe the issue here was that you didn't instantiate the potential. That is, you probably tried to do</p>
<pre><code>from galpy.potential import LogarithmicHaloPotential, evaluatePotentials
evaluatePotentials(LogarithmicHaloPotential,1.,0.)
</code></pre>
<p>rather than</p>
<pre><code>from galpy.potential import LogarithmicHaloPotential, evaluatePotentials
lp= LogarithmicHaloPotential() # specific instance with default parameters
evaluatePotentials(lp,1.,0.)
</code></pre>
<p>Please don't hesitate to open an Issue or Discussion at the GitHub page or join the slack community there: <a href="https://github.com/jobovy/galpy" rel="nofollow noreferrer">https://github.com/jobovy/galpy</a>. I don't usually monitor stackexchange.</p>

CC BY-SA 4.0
2022-06-28T02:04:15.767Z
*Welcome to Astronomy SE!*
uhoh
CC BY-SA 4.0
2022-06-28T00:16:33.220Z
2022-06-28T00:18:00.550Z
2022-06-28T00:18:00.550Z
Jo Bovy
<p>I am trying to model galactic disks. From the past research we have discovered that the halo follows the logarithmic potential, the disk follows the Miyamoto-Nagai potential and the bulge follows the Hernquist potential. I have the <span class="math-container">$R$</span> and <span class="math-container">$z$</span> coordinates of a sample of stars divided into halo, bulge and disk stars and I am trying to compute the potentials of these potential using <a href="https://github.com/jobovy/galpy" rel="nofollow noreferrer">galpy</a>'s <code>galpy.potential.evaluatePotentials(Pot, R, z, phi=None, t=0.0, dR=0, dphi=0)</code>.</p>
<p>However, it looks like the potentials are defaulted as non axis symmetric during initialization since I am getting the error message as shown in the image.</p>
<p><a href="https://i.sstatic.net/dPnwD.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/dPnwD.png" alt="enter image description here" /></a></p>
<p>Is there a way to make this work?</p>
<p>Coding the potentials is one way to get around the problem, however, before resorting to this option, I needed to check whether there are solutions available already.</p>
<p>Cheers!!!</p>

CC BY-SA 4.0
2022-06-23T23:05:35.143Z
Never used `galpy` before and not sure how your doing your import and definition (can you edit the Q to show this please?) but if I do a `from galpy.potential import LogarithmicHaloPotential ; halo = LogarithmicHaloPotential()` then doing a `halo.isNonAxi` returns False so it has that attribute.
astrosnapper
CC BY-SA 4.0
2022-06-24T13:25:03.497Z
Looks like a temporary bug in the code. I uninstalled galpy and reinstalled it. That worked!!!
CTZenScientist
<galaxy><python><galactic-dynamics><galactic-halo><galactic-evolution>
Evaluating Potentials using Galpy
CTZenScientist
# Evaluating Potentials using Galpy

(Asked by: username_0 on 2022-06-23)

I am trying to model galactic disks. From the past research we have discovered that the halo follows the logarithmic potential, the disk follows the Miyamoto-Nagai potential and the bulge follows the Hernquist potential. I have the $R$ and $z$ coordinates of a sample of stars divided into halo, bulge and disk stars and I am trying to compute the potentials of these potential using [galpy](https://github.com/username_2/galpy)'s `galpy.potential.evaluatePotentials(Pot, R, z, phi=None, t=0.0, dR=0, dphi=0)`.

However, it looks like the potentials are defaulted as non axis symmetric during initialization since I am getting the error message as shown in the image.

[![enter image description here](https://i.sstatic.net/dPnwD.png)](https://i.sstatic.net/dPnwD.png)

Is there a way to make this work?

Coding the potentials is one way to get around the problem, however, before resorting to this option, I needed to check whether there are solutions available already.

Cheers!!!

**Tags:** galaxy, python, galactic-dynamics, galactic-halo, galactic-evolution

> **Comments:**
> **username_1**: Never used `galpy` before and not sure how your doing your import and definition (can you edit the Q to show this please?) but if I do a `from galpy.potential import LogarithmicHaloPotential ; halo = LogarithmicHaloPotential()` then doing a `halo.isNonAxi` returns False so it has that attribute.  
> **username_0**: Looks like a temporary bug in the code. I uninstalled galpy and reinstalled it. That worked!!!  

---

## 1 answers

### Answer by username_2 on 2022-06-28. Score: 3 | Accepted answer

For future reference, I believe the issue here was that you didn't instantiate the potential. That is, you probably tried to do

```
from galpy.potential import LogarithmicHaloPotential, evaluatePotentials
evaluatePotentials(LogarithmicHaloPotential,1.,0.)

```

rather than

```
from galpy.potential import LogarithmicHaloPotential, evaluatePotentials
lp= LogarithmicHaloPotential() # specific instance with default parameters
evaluatePotentials(lp,1.,0.)

```

Please don't hesitate to open an Issue or Discussion at the GitHub page or join the slack community there: <https://github.com/username_2/galpy>. I don't usually monitor stackexchange.

> **Comments:**
> **username_3**: *Welcome to Astronomy SE!*  

---

