bug fix: column specification for shuffle

pipeline.py

@@ -224,12 +224,13 @@ class Components :
 		if 'ignore' in args and 'columns' in args['ignore'] :
 			_cols = self.get_ignore(data=df,columns=args['ignore']['columns'])
 		
-
-		for name in list (set(df.columns) - set(_cols)) :
+		columns = args['columns'] if 'columns' in args else df.columns
+		columns = list(set(columns) - set(_cols))
+		for name in columns :
 			i = np.arange(df.shape[0])
 			np.random.shuffle(i)
 			if name in x_cols :
-				df[name] = self.approximate(df[name].values)
+				df[name] = self.approximate(df.iloc[i][name].values)
 			df[name] = df.iloc[i][name]
 		self.post(data=df,schema=schema,store=args['store']['target'])	
 	def post(self,**_args) :