difmap

Description

difmap performs arithmetic operations or linear combinations over maps with the same resolution. difmap can display basic map information (resolution, maximum/minimum temperature values and positions), simple statistics: mean and variance, the histogram of pixel values of the map, and the number of pixels on a given temperature interval. difmap can also rotate the map in $\phi$ and/or $\theta$ direction, or convert the map from Galactic to equatorial coordinate base.

Examples

1. Display statistics:
   • difmap map.fits -st
     displays basic information and simple statistics of the map ' map.fits'.

   • difmap map.fits -st -hf map.histo.txt -hn 200
     bins the pixels values of the map ' map.fits' for its histogram. The number of the bin is set 200 and the ASCII histogram is output to ' map.histo.txt'.

   • difmap map.fits -st -lev 1. -eps 0.3
     displays basic information, simple statistics of the map ' map.fits'. Also shown is the number of pixels between temperature interval [0.7,1.3].

   • difmap -cor map1.fits map2.fits
     displays the cross-correlation coefficients of two maps ' map1.fits' and ' map2.fits'.

2. Arithmetic operations:
   • difmap -c1 1.5 map.fits -o out.fits
     multiplies all pixel values from file ' map.fits' by a factor of 1.5 and outputs to ' out.fits'.

   • difmap -c1 0.5 -c2 0.6 map1.fits map2.fits -o out.fits
     multiplies the map ' map1.fits' by 0.5 and ' map2.fits' by 0.6 and outputs the resultant map to ' out.fits'. The operation can be expressed as map.out = 0.5 * map1 - 0.6 * map2.

3. Map rotation:
   • difmap -dt 0.5 map.fits -o map.rot.fits
     rotates the map ' map.fits' in $\theta$ direction by 0.5 (rad) and outputs to ' map.rot.fits'.

   • difmap -dp 1.2 -dt 0.7 map.fits -o map.rot.fits
     rotates the map ' map.fits' in $\phi$ direction by 1.2 (rad) followed by in $\theta$ by 0.7 (rad) and outputs to ' map.rot.fits'.

4. Masking:
   • difmap map.k.fits -mf kp2.glesp.fits -o map.k.mask.fits -du 1.e4
     masks the WMAP K-band map ' map.k.fits' with the WMAP kp2 mask ' kp2.glesp.fits' (both in GLESP format). The values of the pixels in the mask are set 10000. The output is in ' map.k.mask.fits'.