What is the use of RANK ?????

Dear All,

I have issues/queries on Machine Learning Projects.
1. How the RANK is functioning what is the use of it???, how can we decide the number to pass in RANK while instantiating object of RandomizedPcaTrainer.??

In my Application

i have density data around 57000 rows

data set column:-
density day month year hour minute second

requirement:- find out inline /out liner density abnormal data

so i have used "RandomizedPcaTrainer" with option parameters.

input column name "Density"
Output column name "Label"

feature column:- day month year hour minute second

SEED=5000
RANK=???

so on which basis i have decide RANK number.

Result will be differ between RANK=3 and RANK=5

so on which basis i have decide RANK???