Table:
0
A
B
C
D
E
F
1
District
Incumbent
Party
First elected
Result
Candidates
2
Virginia 2
James Trezvant
Jacksonian
1825
Re-elected
James Trezvant (J) 100%
3
Virginia 3
William S. Archer
Jacksonian
1820 (special)
Re-elected
William S. Archer (J) 100%
4
Virginia 4
Mark Alexander
Jacksonian
1819
Re-elected
Mark Alexander (J) 100%
5
Virginia 5
George W. Crump
Jacksonian
1826 ( special )
Retired Jacksonian hold
John Randolph (J) 100%
6
Virginia 6
Thomas Davenport
Jacksonian
1825
Re-elected
Thomas Davenport (J) 100%
7
Virginia 8
Burwell Bassett
Jacksonian
1805 1821
Re-elected
Burwell Bassett (J) 100%
8
Virginia 9
Andrew Stevenson
Jacksonian
1821
Re-elected
Andrew Stevenson (J) 100%
9
Virginia 10
William C. Rives
Jacksonian
1823
Re-elected
William C. Rives (J) 100%
10
Virginia 11
Robert Taylor
Adams
1825
Retired Jacksonian gain
Philip P. Barbour (J) 100%
11
Virginia 12
Robert S. Garnett
Jacksonian
1817
Retired Jacksonian hold
John Roane (J) 100%
12
Virginia 14
Charles F. Mercer
Adams
1817
Re-elected
Charles F. Mercer (A) 63.0% Robert Thompson 37.0%
13
Virginia 15
John S. Barbour
Jacksonian
1823
Re-elected
John S. Barbour (J) 65.0% William E. Hunton 35.0%
14
Virginia 16
William Armstrong
Adams
1825
Re-elected
William Armstrong (A) 78.0% John Peters 22.0%
15
Virginia 19
William McCoy
Jacksonian
1811
Re-elected
William McCoy (J)
16
Virginia 20
John Floyd
Jacksonian
1817
Re-elected
John Floyd (J) 87.2% Edward Watts 12.8%

Questions and formulas:
Question: How many district has a candidate that was first elected on 1811?
Formula: ROWS(UNIQUE(FILTER(A1, D1=1811)))
Formula2: ROWS(UNIQUE(FILTER(A2:A16, D2:D16=1811)))
Level: medium