fixed a bug in the heatmap code

1 job for master in 1 minute and 2 seconds (queued for 2 seconds)
Name Stage Failure
failed
test Test There is an unknown failure, please try again
  Downloading pycryptodomex-3.4.6.tar.gz (6.5MB)
Collecting rpy2 (from fractalis==0.0.0)
Downloading rpy2-2.8.6.tar.gz (191kB)
Complete output from command python setup.py egg_info:
Error: Tried to guess R's HOME but no command 'R' in the PATH.

----------------------------------------
Command "python setup.py egg_info" failed with error code 1 in /tmp/pip-build-nax9vhl5/rpy2/
ERROR: Job failed: exit code 1