Added erf function (TANGODEVIC-1843)

Data not reset in case of no fit convergence (TANGODEVIC-1842)

src/DataFitterTask.cpp

@@ -631,13 +631,12 @@ DataFitterTask::FitStatus DataFitterTask::dofit()
     break;
     }
 
-    //debut TANGODEVIC-1263
-    if (ret_val.state != Tango::RUNNING)
+	// Add condition to avoid data reset when fit does not converge
+	if ((ret_val.state != Tango::RUNNING) && (status != GSL_CONTINUE))
 	{
         this->reset_data();
 		return ret_val;
     }
-    //fin TANGODEVIC-1263
 
     if ( config_.fit_params.auto_guess )
     {

src/DataFitterTask.h

@@ -62,6 +62,8 @@ struct tango_string
 };
 
 // initial parameters of the fit
+// Nota: for parameters of the KnifeEdge(x) function: "mu" is associated to "position"
+// "sigma" is associated to "width"
 struct Params
 {
     Params()