rpy2 'knn' analysis error: too many ties in knn

Question

I keep getting the same error during knn analysis of a 1-dimensional data set. The function is presented below:

def KNN(data,legend):

    importr('class') #package for knn object

    print data #both DataFrame objects
    print legend

    KNN_result=robjects.r('knn')(data,data,legend,1) #k=1

The output as follows (firstly: data):

    attribute
1               0
2               0
3               1

...

1635            0
1636            1

And now the legend:

   [1] A A A A B B B B  

...

[1633] A A A A
Levels: A B

The error:

Error in function (train, test, cl, k = 1, l = 0, prob = FALSE, use.all = TRUE)  : 
  too many ties in knn

Can anybody please help ? Importantly -if the data are not binary, but range from 0 to 1 as float numbers the error does not appear and i can analyze the data correctly.