ZH: figlib: report chi**2 when fitting

simulations/airshower_beacon_simulation/lib/figlib.py

@@ -98,6 +98,7 @@ def phase_comparison_figure(
 def fitted_histogram_figure(
         amplitudes,
         fit_distr = None,
+        calc_chisq = True,
         text_kwargs={},
         hist_kwargs={},
         mean_snr = None,
@@ -169,6 +170,14 @@ def fitted_histogram_figure(
 
             ax.plot(xs, fit_ys*scale, label=label)
 
+            chisq_strs = []
+            if calc_chisq:
+                ct = np.diff(distr_func.cdf(bins, *fit_params))*np.sum(counts)
+                c2t = stats.chisquare(counts, ct, ddof=len(fit_params))
+                chisq_strs = [
+                        f"$\\chi^2$/dof = {c2t[0]: .2g}/{len(fit_params)}"
+                        ]
+
             # change parameters if needed
             text_fit_params = fit_params2text_params(fit_params)
 
@@ -176,6 +185,8 @@ def fitted_histogram_figure(
                 [label]
                 +
                 [ f"{param} = {value: .2e}" for param, value in zip_longest(param_names, text_fit_params, fillvalue='?') ]
+                +
+                chisq_strs
                 )
 
             this_info = {
@@ -185,6 +196,10 @@ def fitted_histogram_figure(
                     'text_str': text_str,
                 }
 
+            if chisq_strs:
+                this_info['chisq'] = c2t[0]
+                this_info['dof'] = len(fit_params)
+
             fit_info.append(this_info)
 
         loc = (0.02, 0.95)