Comments (4)
Hi @rmjarvis -
Thanks for pointing this out. I feel like we have touched on this a few times verbally but never written something down.
I just took a look at piff.util.calculate_moments()
. It looks pretty good to me for setting up higher moments measurement. I just have a few questions and comments:
- I have a hard time lining up the index of M_{pq} in piff with its mathematical meaning: for example, for second moments, M11=trace, M20=e1, M02=e2. I don't think we need to change how the indices are done here, as that could break some other code, but maybe we need some explanation for the indices.
- Here du and dv are coordinated from the centroid. So the higher moments will be correlated to second moments (larger PSF = larger higher radial moments, for example). This is slightly different from the definition that I have been using, which erases the second moment's information. I think both definitions are probably fine for capturing additive biases in shear, but I need to look at their difference with a certain dataset to say that for sure.
As in the name, I agree T4 and e4 are much easier to understand. I would still suggest adding a parenthesis, i.e., T^(4) and e^(4) to avoid confusion with the power of the second moments. I am open to suggestions too.
from piff.
I agree that the naming scheme for the M's in calculate_moments is a bit non-standard. I think the notation came from @aaronroodman. But it's trying to hew closer to the "spin" combinations. Here is the logic of it.
For p>=q:
M_pq = Re(<(u+iv)^p (u-iv)^q>)
M_qp = Im(<(u+iv)^p (u-iv)^q>)
So M_20 is aka e_1. M_02 is e_2. M11 is T.
At fourth order, M_22 is the spin-0 quantity. M_31 + iM_13 is spin-2. And M_40 + iM04 is spin-4.
from piff.
from piff.
PR here: #144
from piff.
Related Issues (20)
- Add calculate_moments function to util and associated unit tests. HOT 1
- PSF wings HOT 2
- Reading WCS solution of ZTF images HOT 1
- Stars Center on the stamps HOT 7
- psf.draw | wcs is not a list for single chip fit HOT 5
- Add equality testing HOT 1
- very large PSF (after re-installation) | Bad fit HOT 6
- regularize in a hacky way HOT 3
- Examples in documentation & `examples/` fail for v1.2 HOT 3
- Piff catastrophically fails when PixelGrid size is larger than input star images HOT 3
- Inconsistent piff log message levels HOT 2
- Fix max_snr weight adjustment.
- Make it easy to run just the star selection without fitting a PSF model
- incorrect error message with missing keyword
- coadd_object_id in psf_stars extension is stored as an f8 instead of an i8 HOT 3
- Let weight, badpix be different files from image.
- Strange PSF fitting HOT 5
- Request: Release new version
- test suite needs pytest<8 and galsim<2.5 HOT 1
Recommend Projects
-
React
A declarative, efficient, and flexible JavaScript library for building user interfaces.
-
Vue.js
🖖 Vue.js is a progressive, incrementally-adoptable JavaScript framework for building UI on the web.
-
Typescript
TypeScript is a superset of JavaScript that compiles to clean JavaScript output.
-
TensorFlow
An Open Source Machine Learning Framework for Everyone
-
Django
The Web framework for perfectionists with deadlines.
-
Laravel
A PHP framework for web artisans
-
D3
Bring data to life with SVG, Canvas and HTML. 📊📈🎉
-
Recommend Topics
-
javascript
JavaScript (JS) is a lightweight interpreted programming language with first-class functions.
-
web
Some thing interesting about web. New door for the world.
-
server
A server is a program made to process requests and deliver data to clients.
-
Machine learning
Machine learning is a way of modeling and interpreting data that allows a piece of software to respond intelligently.
-
Visualization
Some thing interesting about visualization, use data art
-
Game
Some thing interesting about game, make everyone happy.
Recommend Org
-
Facebook
We are working to build community through open source technology. NB: members must have two-factor auth.
-
Microsoft
Open source projects and samples from Microsoft.
-
Google
Google ❤️ Open Source for everyone.
-
Alibaba
Alibaba Open Source for everyone
-
D3
Data-Driven Documents codes.
-
Tencent
China tencent open source team.
from piff.