change index to ng

droplet_growth/fit.py

@@ -268,14 +268,16 @@ def hill(x, n, K):
 def erf_fun(x, a, b):
     return ((1 + erf(a * (x - b))) / 2)
 
-def fit_sigmoid(probs, ax, fun=sigmoid, fit_name='sigmoid', p0=(2., -2.)):
+def fit_sigmoid(probs, ax=None, fun=sigmoid, fit_name='sigmoid', p0=(2., -2.)):
     probs = probs.copy()
-    vector = probs.index
+    vector = probs.ng
 #     print(vector)
 #     probs.loc[:, 'negative'] = 1 - probs.positive
     popt, pcov = curve_fit(fun, vector, probs.q, p0=p0)
     a, b = popt
     da, db = np.sqrt(np.diag(pcov))
+    if ax is None:
+        fig, ax = plt.subplots()
     ax.plot(vector, probs.q, '.', label='data')
     ax.plot((x := sorted(vector)), fun(x, *popt), lw=10, alpha=.5, label=f'{fit_name} fit')
     plt.legend()