bugfix in plot legend

eda/ml_tools/rate.csv

@@ -2,4 +2,5 @@ date,answer_imp_all,answer_imp_ios,answer_imp_android,diary_imp_all,diary_imp_io
 20180817,0.0401,0.0569,0.0336,0.7272,0.8801,0.6678,0.0403,0.0624,0.0269,59.93,92.74,0.0189,0.0178,0.02,0.1094,0.1391,0.0852,0.1242,0.1537,0.1
 20180818,0.0383,0.0526,0.0331,0.7134,0.8665,0.658,0.0414,0.065,0.0267,57.73,78.98,0.0153,0.0167,0.0139,0.1052,0.1397,0.0786,0.1227,0.1572,0.0972
 20180819,0.0393,0.0538,0.0337,0.7211,0.8763,0.6605,0.0468,0.0726,0.0293,51.29,73.27,0.0175,0.0212,0.0136,0.1115,0.1442,0.085,0.1283,0.1598,0.1027
-20180820,0.0374,0.0504,0.032,0.7443,0.8829,0.6866,0.0449,0.068,0.0281,55.88,84.81,0.0157,0.0192,0.0118,0.1142,0.149,0.0846,0.1284,0.1641,0.0981
\ No newline at end of file
+20180820,0.0374,0.0504,0.032,0.7443,0.8829,0.6866,0.0449,0.068,0.0281,55.88,84.81,0.0157,0.0192,0.0118,0.1142,0.149,0.0846,0.1284,0.1641,0.0981
+20180821,0.0376,0.0509,0.0322,0.7392,0.8783,0.6831,0.0429,0.0658,0.0274,58.85,90.43,0.0174,0.0185,0.0162,0.1162,0.1551,0.0846,0.1316,0.1709,0.0998