Frequently Asked Questions

This page provides answers to common questions about Sherpa functionality; feel free to submit a new one via the CXC Helpdesk.

General

Command Comparison

1. What is the difference between the 'load', 'read', and 'unpack' Sherpa commands?
2. What do the Sherpa 'get' commands do?
3. How do Sherpa 'load' commands handle ASCII files?
4. How can I convert my Sherpa 3.4 scripts to Sherpa 4.1?

Plotting

1. How can I modify a single plot in a display containing multiple plots?
2. How can I plot a spectrum in photon flux units (photons s^-1 cm^-2 keV^-1)?

Parameter Estimation

1. What does it mean when "----" appears for a parameter upper or lower limit in the projection or covariance output?