Table:
0
A
B
C
D
E
1
State (class)
Vacator
Reason for change
Successor
Date of successors formal installation
2
Alabama (2)
New seats
Alabama was admitted to the Union.
John W. Walker (DR)
Elected December 14, 1819
3
Alabama (3)
New seats
Alabama was admitted to the Union.
William R. King (DR)
Elected December 14, 1819
4
Maine (2)
New seats
Maine was admitted to the Union.
John Holmes (F)
Elected June 13, 1820
5
Maine (1)
New seats
Maine was admitted to the Union.
John Chandler (DR)
Elected June 14, 1820
6
Maryland (1)
Alexander C. Hanson (F)
Died April 23, 1819
William Pinkney (DR)
Elected December 21, 1819
7
Virginia (2)
John W. Eppes (DR)
Resigned December 4, 1819
James Pleasants (DR)
Elected December 10, 1819
8
Massachusetts (1)
Prentiss Mellen (F)
Resigned May 15, 1820
Elijah H. Mills (F)
Elected June 12, 1820
9
Rhode Island (2)
James Burrill, Jr. (F)
Died December 25, 1820
Nehemiah R. Knight (DR)
Elected January 9, 1821

Questions and formulas:
Question: Who was the successor for the state of Maine (2) ?
Formula: UNIQUE(CHOOSECOLS(FILTER(A1:E1,A1="Maine (2)"),4))
Formula2: UNIQUE(CHOOSECOLS(FILTER(A2:E9,A2:A9="Maine (2)"),4))
Level: medium
Question: What is the date of successors formal installation when the reason for change is resigned december 4, 1819?
Formula: UNIQUE(CHOOSECOLS(FILTER(A1:E1,C1="Resigned December 4, 1819"),5))
Formula2: UNIQUE(CHOOSECOLS(FILTER(A2:E9,C2:C9="Resigned December 4, 1819"),5))
Level: medium
Question: How many entries are shown for date of successors formal installation where successor is john w. walker (dr)?
Formula: UNIQUE(CHOOSECOLS(FILTER(A1:E1,D1="John W. Walker (DR)"),5))
Formula2: UNIQUE(CHOOSECOLS(FILTER(A2:E9,D2:D9="John W. Walker (DR)"),5))
Level: medium
Question: Who was the successor for the state (class) of maine (2)?
Formula: UNIQUE(CHOOSECOLS(FILTER(A1:E1,A1="Maine (2)"),4))
Formula2: UNIQUE(CHOOSECOLS(FILTER(A2:E9,A2:A9="Maine (2)"),4))
Level: medium
Question: what is the state for reason for change is resigned may 15, 1820?
Formula: UNIQUE(CHOOSECOLS(FILTER(A1:E1,C1="Resigned May 15, 1820"),1))
Formula2: UNIQUE(CHOOSECOLS(FILTER(A2:E9,C2:C9="Resigned May 15, 1820"),1))
Level: medium