Handle zero parameter errors in ctulimit (#1795)

Jürgen Knödlseder
1 parent 2ee8bac1
Showing 4 changed files with 15 additions and 5 deletions
ChangeLog
NEWS
README.md
src/ctulimit/ctulimit.cpp
@@ -3,6 +3,7 @@
         * Version 1.1.0 released
         ========================
+        Handle zero parameter errors in ctulimit (#1795)
         Compute counts cube weights in ctbin (#1789)
         Adapt to new stacked cube interface (#1788)
         Add ctools and cscripts unit tests
@@ -183,6 +183,9 @@ ctulimit - Compute upper limit
 Add "edispcube" parameter to support energy dispersion for stacked analysis
 (#1724).
+In case that the parameter error is zero, the parameter value is taken as
+parameter error to define the bracketing parameter values (#1795).
+
 cterror - Likelihood profile error computation
 ----------------------------------------------
 ctools information
 ==================
-* Version:             1.1.0.dev1 (20 June 2016)
+* Version:             1.1.0.dev1 (21 June 2016)
 * Author:              Juergen Knoedlseder (jurgen.knodlseder@irap.omp.eu)
 * GammaLib dependency: 1.1.0.dev1
@@ -290,14 +290,20 @@ void ctulimit::run(void)
     } // endif: likelihood was zero
-    // Extract current value
+    // Extract current value and error
     double value = m_model_par->factor_value();
+    double error = m_model_par->factor_error();
-    // Compute parameter bracketing
+    // If parameter error is zero then take parameter value as error
+    if (error == 0) {
+        error = value;
+    }
+
+    // Compute parameter bracketing. In case that the parameter error is
     double parmin = std::max(m_model_par->factor_min(),
-                             value - m_sigma_min * m_model_par->factor_error());
+                             value - m_sigma_min * error);
     double parmax = std::min(m_model_par->factor_max(),
-                             value + m_sigma_max * m_model_par->factor_error());
+                             value + m_sigma_max * error);
     // Write header
     if (logTerse()) {