Hi, This is a question regarding how "fit_counts" uses the initial parameter values given by "list_par". This is a summary of what I am doing / what is happening: - load data with NULL response and NULL arf - fit with "gaussian" using Cash statistic - use "conf" to find the 68% confidence limit for "gaussian(1).LineE" - ISIS tells me an improved fit has been found - "list_par" shows the new best fit parameters - and "eval_counts" shows that these parameters indeed give a better fit so far so good - but, running "fit_counts", the result is a *worse* fit than before (reverting to parameter values similar to those *before* running "conf" My question is: does "fit_counts" use the parameter values shown by "list_par" as starting values for the fit process? If so, how can "fit_counts" find best fit values which give a worse fit than the starting values? Below is the line-by-line interactive session; the data.txt file (gzipped) is attached. Thanks, - Michael isis> load_dataset("data.txt",NULL,NULL); isis> plot_unit("keV"); isis> fit_fun("gaussian(1)"); Solar Abundance Vector set to angr: Anders E. & Grevesse N. Geochimica et Cosmochimica Acta 53, 197 (1989) Cross Section Table set to bcmc: Balucinska-Church and McCammon, 1998 isis> set_par("gaussian(1).norm",380,0); isis> set_par("gaussian(1).LineE",1.465,0); isis> set_par("gaussian(1).Sigma",0.045,0,1e-9,100); isis> set_fit_statistic("cash"); isis> fit_counts; Parameters[Variable] = 3[3] Data bins = 41 Cash Statistic = 38.08494 Reduced Cash Statistic = 1.002235 0 isis> list_par; gaussian(1) idx param tie-to freeze value min max 1 gaussian(1).norm 0 0 464.1966 0 1e+10 2 gaussian(1).LineE 0 0 1.468121 0 1000000 keV 3 gaussian(1).Sigma 0 0 0.05341799 1e-09 100 keV isis> conf("gaussian(1).LineE",0); Found improved fit, stat= 36.8477 for param[2] = 1.47003 **** Found improved fit 1.47003 1.47003 isis> list_par; gaussian(1) idx param tie-to freeze value min max 1 gaussian(1).norm 0 0 470.9957 0 1e+10 2 gaussian(1).LineE 0 0 1.470028 0 1000000 keV 3 gaussian(1).Sigma 0 0 0.05389743 1e-09 100 keV isis> eval_counts; Parameters[Variable] = 3[3] Data bins = 41 Cash Statistic = 36.8477 Reduced Cash Statistic = 0.9696763 0 isis> fit_counts; Parameters[Variable] = 3[3] Data bins = 41 Cash Statistic = 37.87679 Reduced Cash Statistic = 0.9967577 0 isis> list_par; gaussian(1) idx param tie-to freeze value min max 1 gaussian(1).norm 0 0 465.4573 0 1e+10 2 gaussian(1).LineE 0 0 1.468354 0 1000000 keV 3 gaussian(1).Sigma 0 0 0.05348169 1e-09 100 keV -- Michael Smith | Michael.Smith_at_email.domain.hidden XMM-Newton SOC, ESA - ESAC, | P.O. Box 78, | Phone: +34 91 8131 342 28691 Villanueva de la Caņada, | Fax: +34 91 8131 322 Madrid, Spain | 34 65 108 108 32 105 115 32 110 117 109 98 101 114 115 34 80 121 116 104 97 103 111 114 97 115 ================================================================================================ This message and any attachments are intended for the use of the addressee or addressees only. The unauthorised disclosure, use, dissemination or copying (either in whole or in part) of its content is prohibited. If you received this message in error, please delete it from your system and notify the sender. E-mails can be altered and their integrity cannot be guaranteed. ESA shall not be liable for any e-mail if modified. ================================================================================================= ---- You received this message because you are subscribed to the isis-users list. To unsubscribe, send a message to isis-users-request_at_email.domain.hiddenwith the first line of the message as: unsubscribe
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