Hi Britton, I tried to use the iterative_center_of_mass callback like this. Since you said it does not require a sphere callback, I assumed that I don't need to specify a sphere.

data_ds = yt.load('RD0008/RedshiftOutput0008')

hc = HaloCatalog(data_ds=data_ds, finder_method='hop')

hc.add_callback("iterative_center_of_mass")

hc.add_filter("quantity_value", "particle_mass", ">", 1e11, "Msun")

hc.create()

I got a error

NameError: global name 'periodic_distance' is not defined

So can you tell me what would be the right way?

Thanks, Jingjing

2015-03-30 15:08 GMT-04:00 Britton Smith brittonsmith@gmail.com:

Hi Jingjing,

To add that function to the HaloCatalog analysis, you need to do the following:

hc.add_callback("sphere_field_max_recenter", "density")

Note, this callback recenters an existing sphere, so you will need to have added a sphere with:

hc.add_callback("sphere")

Make sure you add the sphere first. Additionally, you might try the "iterative_center_of_mass" callback, which will calculate new centers by calculating the center of mass on a continually smaller sphere. This one does not require a sphere callback and will actually write out the recentered positions.

Britton

On Mon, Mar 30, 2015 at 7:27 PM, Chen Jingjing chenjj235@gmail.com wrote:

...

Dear yt-users, I am having a little problem on finding the exact center of a halo. I used to do

"hc = HaloCatalog(data_ds=data_ds, finder_method='hop')"

to create a halo catalog. But I think the position in the catalog is a little bit off the exact center judging from the plots I made. I need the exact center to compute the angular momentum so the off-center result could cause some problem. I tried to recenter at the maximum gas density by adding this line

"hc.sphere_field_max_recenter('density')"

But I got an error, AttributeError: 'HaloCatalog' object has no attribute 'sphere_field_max_recenter'.

Can anyone tell me what is the right way to find the center as the location of maximum gas density?

Thanks, Jingjing

--

Jingjing Chen [ chenjj235@gmail.com ] Department of Astronomy Columbia University 550 West 120th Street New York, New York 10027 Cell Phone: +1(347)5746709

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Works perfectly! Thank you so much!

Jingjing

2015-03-31 4:12 GMT-04:00 Britton Smith brittonsmith@gmail.com:

Hi Jingjing,

This is a bug that I thought I had fixed already. The file is just missing an import of that function. I have issued a pull request to fix this and it should be incorporated shortly. Sorry about that.

Britton

On Tue, Mar 31, 2015 at 1:55 AM, Chen Jingjing chenjj235@gmail.com wrote:

...

Hi Britton, I tried to use the iterative_center_of_mass callback like this. Since you said it does not require a sphere callback, I assumed that I don't need to specify a sphere.

data_ds = yt.load('RD0008/RedshiftOutput0008')

hc = HaloCatalog(data_ds=data_ds, finder_method='hop')

hc.add_callback("iterative_center_of_mass")

hc.add_filter("quantity_value", "particle_mass", ">", 1e11, "Msun")

hc.create()

I got a error

NameError: global name 'periodic_distance' is not defined

So can you tell me what would be the right way?

Thanks, Jingjing

2015-03-30 15:08 GMT-04:00 Britton Smith brittonsmith@gmail.com:

Hi Jingjing,

...

To add that function to the HaloCatalog analysis, you need to do the following:

hc.add_callback("sphere_field_max_recenter", "density")

Note, this callback recenters an existing sphere, so you will need to have added a sphere with:

hc.add_callback("sphere")

Make sure you add the sphere first. Additionally, you might try the "iterative_center_of_mass" callback, which will calculate new centers by calculating the center of mass on a continually smaller sphere. This one does not require a sphere callback and will actually write out the recentered positions.

Britton

On Mon, Mar 30, 2015 at 7:27 PM, Chen Jingjing chenjj235@gmail.com wrote:

...

Dear yt-users, I am having a little problem on finding the exact center of a halo. I used to do

"hc = HaloCatalog(data_ds=data_ds, finder_method='hop')"

to create a halo catalog. But I think the position in the catalog is a little bit off the exact center judging from the plots I made. I need the exact center to compute the angular momentum so the off-center result could cause some problem. I tried to recenter at the maximum gas density by adding this line

"hc.sphere_field_max_recenter('density')"

But I got an error, AttributeError: 'HaloCatalog' object has no attribute 'sphere_field_max_recenter'.

Can anyone tell me what is the right way to find the center as the location of maximum gas density?

Thanks, Jingjing

--

Jingjing Chen [ chenjj235@gmail.com ] Department of Astronomy Columbia University 550 West 120th Street New York, New York 10027 Cell Phone: +1(347)5746709

---

yt-users mailing list yt-users@lists.spacepope.org http://lists.spacepope.org/listinfo.cgi/yt-users-spacepope.org

---

yt-users mailing list yt-users@lists.spacepope.org http://lists.spacepope.org/listinfo.cgi/yt-users-spacepope.org

--

Jingjing Chen [ chenjj235@gmail.com ] Department of Astronomy Columbia University 550 West 120th Street New York, New York 10027 Cell Phone: +1(347)5746709

---

yt-users mailing list yt-users@lists.spacepope.org http://lists.spacepope.org/listinfo.cgi/yt-users-spacepope.org

---

yt-users mailing list yt-users@lists.spacepope.org http://lists.spacepope.org/listinfo.cgi/yt-users-spacepope.org