rstub/swephr-debug repository overview

⁠swephR

The goal of swephR is to provide an R interface to the Swiss Ephemeris⁠. The Swiss Ephemeris is a high precision ephemeris based upon the DE431 ephemeris from NASA’s JPL. It covers the time range 13201 BCE to 17191 CE.

⁠Installation

You can install the released version of swephR from CRAN⁠ with:

install.packages("swephR")

Intermediate releases can also be obtained via drat⁠:

if (!requireNamespace("drat", quietly = TRUE)) install.packages("drat")
drat::addRepo("rstub")
install.packages("swephR")

This package uses the semi-analytic theory by Steve Moshier. For faster and more accurate calculations, the compressed Swiss Ephemeris data is available in the swephRdata package. To access this data package, run

install.packages("swephRdata", repos = "https://rstub.github.io/drat/", type = "source")

The size of the swephRdata package is approximately 115 MB. The user can also use the original JPL DE431 data.

⁠Example

To compute the position of celestial body or star with SE (Swiss Ephemeris), you do the following steps:

library(swephR)
swe_version()
#> [1] "2.08"

For a specific date, compute the Julian day number (in below example: J2000.0, 1 January 2000 at 12:00 UT):

year <- 2000
month <- 1
day <- 1
hour <- 12
jdut <- swe_julday(year, month, day, hour, SE$GREG_CAL)
jdut
#> [1] 2451545

Compute (using Moshier ephemeris) the positions (longitude, latitude, distance, longitude speed and latitude speed) of a planet or other celestial bodies (in below example: the Sun):

ipl <- SE$SUN
iflag <- SE$FLG_MOSEPH + SE$FLG_SPEED
result <- swe_calc_ut(jdut, ipl, iflag)
result
#> $return
#> [1] 260
#> 
#> $xx
#> [1]  2.803689e+02  2.323265e-04  9.833276e-01  1.019432e+00 -8.922802e-07
#> [6] -7.339410e-06
#> 
#> $serr
#> [1] ""

or a fixed star (in below example: Sirius):

starname = "sirius"
result <- swe_fixstar2_ut(starname, jdut, iflag)
result
#> $return
#> [1] 260
#> 
#> $starname
#> [1] "Sirius,alCMa"
#> 
#> $xx
#> [1]  1.040853e+02 -3.960507e+01  5.439322e+05  4.643164e-05 -7.119376e-05
#> [6] -4.130539e-03
#> 
#> $serr
#> [1] ""

The current R interface is modeled after the C interface. It is therefore often helpful to consult the general documentation⁠ and programmer’s documentation⁠ for the Swiss Ephemeris.

⁠Feedback

All feedback (bug reports, security issues, feature requests, …) should be provided as issues⁠.