How to convert type Row into Vector to feed to the KMeans

when i try to feed df2 to kmeans i get the following error

clusters = KMeans.train(df2, 10, maxIterations=30,
                        runs=10, initializationMode="random")

The error i get:

Cannot convert type <class 'pyspark.sql.types.Row'> into Vector

df2 is a dataframe created as follow:

df = sqlContext.read.json("data/ALS3.json")
df2 = df.select('latitude','longitude')

df2.show()


     latitude|       longitude|

   60.1643075|      24.9460844|
   60.4686748|      22.2774728|

how can i convert this two columns to Vector and feed it to KMeans?