I want to transpose a table (interchange rows to columns and vice versa). How to do that in iWork Numbers.
I wrote a simple AppleScript that does it.
tell application "Numbers"
activate
tell the front document
tell the first sheet
set original_range to selection range of first table
set orignal_table to first table
set number_of_columns to column count of orignal_table
set number_of_rows to row count of orignal_table
set trasposed_table to make new table with properties {row count:number_of_columns, column count:number_of_rows}
repeat with i from 1 to number_of_columns
repeat with j from 1 to number_of_rows
tell orignal_table
set original_value to the value of cell i of row j
end tell
tell trasposed_table
set the value of cell j of row i to original_value
end tell
end repeat
end repeat
end tell
end tell
end tell
Here you can find more details about it.

2It's worth mentioning this formula takes the cells'
value
meaning that if you have formulas in the cells you are transposing, only their output will be transposed. The formulas will not be. – Nick Q. Dec 19 '12 at 0:03
Those using the latest version of Numbers can use the "Transpose Rows and Columns" option under the "Table" menu, as seen in this answer over on StackExchange. Image below also shamelessly 'borrowed' from that answer, for easy reference.