diff --git a/wwdata/Class_HydroData.py b/wwdata/Class_HydroData.py
index 51013c40e..c6e73a7ae 100644
--- a/wwdata/Class_HydroData.py
+++ b/wwdata/Class_HydroData.py
@@ -1451,6 +1451,9 @@ def get_correlation(self,data_1,data_2,arange,zero_intercept=False,
             default to 'False'
             if a value in one column is filtered, the corresponding value in the second
             column also gets excluded!
+        plot : bool
+            if true, a plot is made, comparing the original data with the calculated
+            prediction
 
         Returns
         -------
@@ -1544,7 +1547,7 @@ def get_correlation(self,data_1,data_2,arange,zero_intercept=False,
 
         return slope,intercept,r_sq
 
-    def detect_drift(self, data_name, arange, max_slope, period=None):
+    def detect_drift(self, data_name, arange, max_slope=None, period=None, plot=False):
         # data input or using self.data?
         """
         This function calculates the slope of the data in a certain given
@@ -1559,8 +1562,10 @@ def detect_drift(self, data_name, arange, max_slope, period=None):
             the range in which to apply the function
         max_slope : int
             the maximum slope a signal is expected to have over a certain period
-        period :
+        period : int
             the period over which a certain slope is allowed
+        plot : bool
+            if true, a plot is made, .......
 
         Returns
         ----------
@@ -1569,20 +1574,44 @@ def detect_drift(self, data_name, arange, max_slope, period=None):
         from scipy import signal
         series = self.data[data_name][arange[0]:arange[1]].copy()
 
+        #removes NaNs and infs from the dataset
+        index = 0
+        nan_values = []
+        for value in series:
+            try:
+                signal.detrend([value])
+            except ValueError:
+                nan_values.append(index)
+            index += 1
+        series = series.drop(index=series[nan_values].index)
+
+        if max_slope is None:
+            print('Please specify a maximum slope')
+            return KeyError
+
         if period is None or period is arange:
+            detrended_values = signal.detrend(series)
+            line_segment = series - detrended_values[:]
+            slope = (int(line_segment[-1]) - int(line_segment[0])) / (arange[1].day - arange[0].day + 1)
 
-            detrended_values = signal.detrend(series[:])
-            line_segment = series[:] - detrended_values[:]
-            slope = (int(line_segment[-1]) - int(line_segment[0])) / len(series)
-            print(slope)
             if slope > max_slope:
-                print('The actual slope is larger than the specified max slope')
-
-            #plt.plot(detrended_values, 'r', series[:], 'g', line_segment, 'y')
+                print('Based on the specified maximum slope, a drift was'
+                      ' detected with a slope higher than the maximum one. \n'
+                      'Slope detected: {}, maximum slope: {}'.format(slope, max_slope))
 
         else:
+            if type(period) is int:
+                for n in range(len(series)-period):
+                    pass
+                pass
+            else:
+                print('period must be an integer')
+                return ValueError
             pass
 
+        if plot is True:
+            print(plt.plot(detrended_values, 'r', line_segment, 'y', series[:], 'g'))
+
         return None