I just started using spark and am trying to run a logistic regression. 
I keep getting this error: 

```
Caused by: java.lang.IllegalArgumentException: requirement failed: 
Dimensions mismatch when adding new sample. Expecting 21 but got 17.

```

The number of features that I have is 21 , but I'm not sure what the 17 means here. Not sure what to do?
My code is here:

```
from pyspark.mllib.regression import LabeledPoint
from numpy import array

def isfloat(string):
   try:
    float(string)
        return True
    except ValueError:
        return False

def parse_interaction(line):
    line_split = line.split(",")
    # leave_out = [1,2,3]
    clean_line_split = line_split[3:24]
    retention = 1.0
    if line_split[0] == '0.0':
       retention = 0.0
    return LabeledPoint(retention, array([map(float,i) for i in clean_line_split if isfloat(i)]))

training_data = raw_data.map(parse_interaction)

from pyspark.mllib.classification import LogisticRegressionWithLBFGS
from time import time

t0 = time()
logit_model = LogisticRegressionWithLBFGS.train(training_data)
tt = time() - t0

print "Classifier trained in {} seconds".format(round(tt,3))

```