Installing and using the IDL interfaces

The Healpix package provides all the routines to read, write and manipulate Healpix maps in IDL. S2LET completes this framework by providing similar routines for the MW sampling. Interfaces for the spherical harmonic and the wavelet transforms are provided for both samplings and allow for the same flexibility as in the C and Matlab code. In particular, S2LET enables to work either with MW of Healpix maps from the FITS files to the output wavelets plotted in Mollweide projection.

To use the IDL interfaces, one must first build the dynamic C library according to the instructions of this page (i.e. by running make dylib). The variable S2LET must be defined in Bash/Shell and point to the root of the S2LET directory so that IDL can find the dynamic library. Note that CFITSIO and HEALPIX are required to support for the Healpix spherical harmonic transform as well as the FITS input-output routines.

Source code documentation

The IDL code is extensively documented and multiple examples are provided to illustrate its use. The documentation for the individual functions can either be found in the code or through the DOC_LIBRARY command in IDL itself. Alternatively, the HTML version of this documentation is available here.

Testing and using the interfaces

Once the dynamic library is built, you may add s2let/main/src/idl in the IDL path in order to run the IDL functions from elsewhere.


A list of the high-level IDL functions, with brief descriptions is given here:

  Compute exact wavelet transform of a MW signal sampled on the sphere

  Exactly reconstuct a MW signal on the sphere from its wavelets

  Read a MW map from a FITS file

  Write a MW map to a FITS file

  Interface to the Fortran function alm2map in Healpix
  (ring ordered, inverse spherical harmonic transform)

  Interface to the Fortran function map2alm in Healpix
  (ring ordered, forward spherical harmonic transform)

  Compute wavelet transform of a Healpix map (ring ordered)

  Reconstuct a Healpix map (ring ordered) on the sphere from its wavelets

  Plot an MW map using Mollweide projection  

To access the documentation for each function in IDL, simply run:

 >> DOC_LIBRARY, "<function>"

where <function> is the function name.


A number of demos are provided to illustrate the use of the idl interface.

  Run and test all functionalties of the wavelet transform (MW sampling)

  Compute and plot wavelets of Earth tomography data
  (full and multi-resolution, MW sampling)

  Compute and plot wavelets of a random CMB simulation
  (Healpix sampling converted into MW)

  Compute and plot wavelets of a random CMB simulation (Healpix sampling)