Problem with using approx functions

[siqixiong56]

I was trying to run the approx functions locally. However, they behaved differently from what's one the tutorial. The approx sum needs 3 arguments and I am not sure what to put in order to approximate. Can someone help me use them? Also, I cannot use error, samplewith...
shark> describe rand5000;
OK
numbers int
Time taken: 0.143 seconds
shark> select approx_sum(numbers) from rand5000;
62.169: [GC (Metadata GC Threshold) 179982K->30429K(1005056K), 0.0271976 secs]
62.196: [Full GC (Metadata GC Threshold) 30429K->19981K(1005056K), 0.0866642 secs]
63.093: [GC (System.gc()) 45909K->21763K(1005056K), 0.0042580 secs]
63.097: [Full GC (System.gc()) 21763K->10910K(1005056K), 0.1983384 secs]
63.299: [GC (System.gc()) 15782K->11078K(1005056K), 0.0017398 secs]
63.301: [Full GC (System.gc()) 11078K->9947K(1005056K), 0.0761869 secs]
FAILED: Error in semantic analysis: Exactly one argument is expected.
shark> select approx_sum(numbers, numbers, numbers) from rand5000;
130.911: [GC (Allocation Failure) 264388K->30538K(1005056K), 0.0253560 secs]
132.398: [GC (Allocation Failure) 292682K->51941K(1005056K), 0.0284526 secs]
132.821: [GC (Allocation Failure) 309431K->30135K(1005056K), 0.0112377 secs]
OK
2471570.0 +/- NaN (99% Confidence)
Time taken: 4.154 seconds