R language utility functions with astronomical application


The R language is a straightforward and powerful language for manipulating, analyzing, and displaying data.   It is free software with releases for Unix, Windows, and Mac operating systems.   The language is in active open-source development by the R Development Core Team of the R Foundation for Statistical Computing, Vienna, Austria, as a language and environment for statistical computing.   More information is available at http://www.R-project.org.

For the code below, comments and bug reports are always welcome; a contact link is at the bottom of the page.

FITS file utilities

readFITS.r reads multi-dimensional arrays (e.g. images and image cubes) and binary tables (bintables).   The function contains sub-functions that can read and parse headers and read image and binatbles independently.  For usage and examples see the comments at the top of the file.  The only known incompleteness is the absence of bit, complex and array descriptor data types for bintables. 

frameFITS.r reads a FITS binatble into an R data frame, using additional code contributed by Eric H. Neilsen, Jr. of the Fermi National Accelerator Laboratory.  Usage and an example are in the comments at the top of the file.

writeFITSim.r writes a multi-dimensional array (e.g. an image or image cube) in integer or float, single or double precision.  For usage and examples see the comments at the top of the file.

FITS is the Flexible Image Transport System, a common file format in astronomy.  Further information, including format specifications and example files, is available at http://fits.gsfc.nasa.gov/ and http://www.cv.nrao.edu/fits/, among other places.

Julian date

dmjd2ut.r converts decimal modified Julian date to UT (or UT with a time offset for local times).  The function contains a general Julian date to UT day conversion sub-function that can be called independently.

ut2dmjd.r converts UT to decimal modified Julian date.  The function contains a general calendar day to Julian day conversion sub-function that can be called independently.

Binning (independent bins, not smoothing)

bin.r is a straightforward but inefficient (it uses a for loop) binning routine that is useful for simple vectors.  For usage see the comments at the top of the file.

binmat.r generates a matrix that, with a matrix multiplication, bins vectors or multiple vectors stored in matrices.  This is efficient for binning large numbers of vectors.  binmat2.r does the same but leaves the size of the original matrix unchanged by repeating elements within the bins.  For usage see the comments at the top of the file.


Code on this page was developed for analyzing instrumental data from the Zpectrometer, an ultrawideband spectrometer for high-redshift galaxy searches with the U.S. National Radio Astronomy Observatory's 100 meter diameter Robert C. Byrd Green Bank Telescope.   The Zpectrometer was supported by National Science Foundation grant AST-0503946.
Questions or comments?  Please contact Andrew Harris.