# Searching for Nearest-Neighbors between Two Coordinate Catalogs

Written by Taro Sato, on . Tagged: stats astro

Say I have two catalogs of points, each in two-dimensional space. For each object in a catalog, I want to find the nearest object(s) in the other catalog. I can do this by computing the distances between every single unique pair of objects and finding the ones within a search radius and possibly doing an additional sort. ... Continue reading.

# Half-Light Radii for Various Profiles

Written by Taro Sato, on . Tagged: astro math

For a radial profile of $$I( r)$$, the enclosed flux within the radius $$r$$ is given by \begin{equation*} F( r) = \int_{0}^{2 \pi} d\phi \int_{0}^{r} dr r I(r, \phi) \ . \end{equation*} I’m only concerned about azimuthal symmetric cases, so $$F( r) = 2\pi \int_{0}^{r} dr r I( r)$$ . ... Continue reading.

# Testing if a Point is Inside a Polygon in Python

Written by Taro Sato, on . Tagged: algo python

Finally got around to finding this out by Googling. Itâ€™s a useful function so I reproduce it here for copy & paste: def inside_polygon(x, y, points): """ Return True if a coordinate (x, y) is inside a polygon defined by the list of verticies [(x1, y1), (x2, y2), . ... Continue reading.