fix array constructor

Author: cwhanse

pvlib/ivtools/sdm.py

@@ -221,7 +221,7 @@ def fit_desoto(v_mp, i_mp, v_oc, i_sc, alpha_sc, beta_voc, cells_in_series,
     # initial guesses of variables for computing convergence:
     # Default values are taken from [2], p753
     init = {}
-    init_guess_keys = ['IL_0', 'Io_0', 'Rs_0', 'Rsh_0', 'a_0']
+    init_guess_keys = ['IL_0', 'Io_0', 'Rs_0', 'Rsh_0', 'a_0']  # order matters
     init['IL_0'] = i_sc
     init['a_0'] = 1.5*k*Tref*cells_in_series
     init['Io_0'] = i_sc * np.exp(-v_oc/init['a_0'])
@@ -233,8 +233,8 @@ def fit_desoto(v_mp, i_mp, v_oc, i_sc, alpha_sc, beta_voc, cells_in_series,
         if k in init_guess_keys:
             init[k] = init_guess[k]
 
-    # params_i : initial values vector
-    params_i = np.array([init_guess[k] for k in init_guess_keys])
+    # params_i : initial values vector, specific order
+    params_i = np.array([init[k] for k in init_guess_keys])
 
     # specs of module
     specs = (i_sc, v_oc, i_mp, v_mp, beta_voc, alpha_sc, EgRef, dEgdT,