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10h
comment Finding planetary conjunctions with Mathematica (project-level)
Point taken, but note the parameter step in that routine: "Step size in seconds for finding angular separation events". In other words, it still appears to be an iterative search.
20h
revised Finding planetary conjunctions with Mathematica (project-level)
added missing definition of `info` variable
20h
asked Finding planetary conjunctions with Mathematica (project-level)
21h
comment Techniques to find all local minima of black box function with n continuous derivatives?
@MichaelE2 Yes, n is at least 6 in all cases. I'm hoping to post more details shortly.
1d
comment Techniques to find all local minima of black box function with n continuous derivatives?
@Guesswhoitis. FindMinmum[] appears to require a starting point, and only finds one minimum. Giving FindMinimum[] (or NMinimize[]) a starting point and finding the minima one at a time seems like it would be slow. At that point, I could simply divide [a,b] into some number of intervals and apply the ternary method on each interval. I was hoping for something faster, which wouldn't require me to choose starting points.
1d
comment Techniques to find all local minima of black box function with n continuous derivatives?
I did look at that first, but it appears to require that f be symbolically differentiable? I might be misreading, so I'll take a closer look.
1d
asked Techniques to find all local minima of black box function with n continuous derivatives?
Aug
28
asked What Method values are available for Plot?
Aug
27
accepted Computing planet conjunctions with 2D circular orbits still hard?
Aug
27
comment Why is AstronomicalData so slow?
It's messy, but github.com/barrycarter/bcapps/tree/master/ASTRO has enough code to compute planetary positions (but you have to download the SPICE kernel files separately). I used this to compute Regulus/Jupiter/Venus conjunctions for astronomy.stackexchange.com/questions/11456/… and to find a 15-year-old bug (now fixed) on the calsky.com site. If there's interest, I can release the .mx dump files, but these are ~300M for every 1000 years of data (and I'm only looking at the visible planets).
Aug
26
comment Why is AstronomicalData so slow?
@Guesswhoitis. Mathematica's AstronomicalData uses a precessing reference frame, and I want ICRF 2000, so rolling my own ephermis is exactly what I'm doing: downloading the SPICE kernels (naif.jpl.nasa.gov/pub/naif/toolkit_docs/C/req/kernel.html), importing them into Mathematica, and then saving them as .mx dump files for faster loading. Seems to help quite a bit.
Aug
25
comment Can I memoize retroactively?
Exactly what I needed, thanks! I was messing around with things like Definition[] but couldn't quite get it to work.
Aug
25
accepted Can I memoize retroactively?
Aug
25
comment Can I memoize retroactively?
I only want to memoize f in a specific file. I don't want to rewrite the definition of f in the file where it's defined. Normally, I would use f without memoization, but, in this one special case, I want to memoize.
Aug
25
asked Can I memoize retroactively?
Aug
16
comment Computing planet conjunctions with 2D circular orbits still hard?
Took me a second to figure out "A better choice is to equate slopes". The slope of a vector (vx,vy) is vy/vx so equating vy/vx=uy/ux for two vectors yields vy*ux = uy*vx, or vy*ux-uy*vx==0
Aug
15
comment Computing planet conjunctions with 2D circular orbits still hard?
Thanks! Edited the question to reflect I'm looking for solutions in t given the constants, and that efficient numerical solutions are fine too.
Aug
15
revised Computing planet conjunctions with 2D circular orbits still hard?
solving for t
Aug
15
asked Computing planet conjunctions with 2D circular orbits still hard?
Aug
8
awarded  Yearling