<html><head><meta http-equiv="Content-Type" content="text/html; charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div class="">I am using the following code to fit a continuum</div><div class=""><br class=""></div><div class=""><font color="#0432ff" class=""><i class="">from astropy.modeling import models</i></font></div><div class=""><font color="#0432ff" class=""><i class="">from astropy.modeling import models, fitting</i></font></div><div class=""><font color="#0432ff" class=""><i class="">from astropy.modeling.models import BlackBody</i></font></div><div class=""><font color="#0432ff" class=""><i class=""><br class=""></i></font></div><div class=""><font color="#0432ff" class=""><i class="">from astropy import units as u</i></font></div><div class=""><font color="#0432ff" class=""><i class=""><br class=""></i></font></div><div class=""><font color="#0432ff" class=""><i class=""><br class=""></i></font></div><div class=""><font color="#0432ff" class=""><i class="">x=x</i></font></div><div class=""><font color="#0432ff" class=""><i class="">y=y</i></font></div><div class=""><font color="#0432ff" class=""><i class=""><br class=""></i></font></div><div class=""><font color="#0432ff" class=""><i class=""><br class=""></i></font></div><div class=""><font color="#0432ff" class=""><i class=""><br class=""></i></font></div><div class=""><font color="#0432ff" class=""><i class="">model_1 = models.PowerLaw1D([1, 1, 1])</i></font></div><div class=""><font color="#0432ff" class=""><i class="">model_2 = models.BlackBody(1800*u.K,5)</i></font></div><div class=""><font color="#0432ff" class=""><i class="">model_1_2=model_1+model_2</i></font></div><div class=""><font color="#0432ff" class=""><i class="">print(model_1_2)</i></font></div><div class=""><font color="#0432ff" class=""><i class=""><br class=""></i></font></div><div class=""><font color="#0432ff" class=""><i class="">def _parameter_units_for_data_units(self, inputs_unit, outputs_unit):</i></font></div><div class=""><font color="#0432ff" class=""><i class=""> return {'amplitude_0': inputs_unit['x'],</i></font></div><div class=""><font color="#0432ff" class=""><i class=""> 'x_0': inputs_unit['x'],</i></font></div><div class=""><font color="#0432ff" class=""><i class=""> 'alpha': inputs_unit['x'],</i></font></div><div class=""><font color="#0432ff" class=""><i class=""> 'temperature': outputs_unit['y'],</i></font></div><div class=""><font color="#0432ff" class=""><i class=""> 'scale_1': inputs_unit['x'] }</i></font></div><div class=""><font color="#0432ff" class=""><i class=""><br class=""></i></font></div><div class=""><font color="#0432ff" class=""><i class=""><br class=""></i></font></div><div class=""><font color="#0432ff" class=""><i class=""># Fit the data using combined model</i></font></div><div class=""><font color="#0432ff" class=""><i class="">g_init = model_1_2(1)</i></font></div><div class=""><font color="#0432ff" class=""><i class="">fit_g = fitting.LevMarLSQFitter()</i></font></div><div class=""><font color="#0432ff" class=""><i class="">g = fit_g(g_init, x, y)</i></font></div><div class=""><font color="#0432ff" class=""><i class=""><br class=""></i></font></div><div class=""><font color="#0432ff" class=""><i class=""># Plot the data with the best-fit model</i></font></div><div class=""><font color="#0432ff" class=""><i class="">plt.figure(figsize=(8,5))</i></font></div><div class=""><font color="#0432ff" class=""><i class="">plt.plot(x, y, 'ko')</i></font></div><div class=""><font color="#0432ff" class=""><i class="">plt.plot(x, t(x), 'b-', lw=2, label='Combined model')</i></font></div><div class=""><font color="#0432ff" class=""><i class=""><br class=""></i></font></div><div class=""><font color="#0432ff" class=""><i class="">plt.xlabel('Wavelength AA')</i></font></div><div class=""><font color="#0432ff" class=""><i class="">plt.ylabel('Flux')</i></font></div><div class=""><font color="#0432ff" class=""><i class="">plt.legend(loc=2)</i></font></div><div class=""><br class=""></div><div class="">x and y are the input data (x: lambda, y: flux) given without units. By definition the blackbody temperature is in Kelvin. This leads to a Unit conversion error in the combined model. Do I have a basic mistake in the code or what is the solution. Any help would be much appreciated.</div><div class="">With kind regards</div><div class="">Rudolf Baer</div><div class=""><br class=""></div></body></html>