CountIf Command
From GeoGebra Manual
 CountIf[ <Condition>, <List> ]
 Counts the number of elements in the list satisfying the condition.
 Example:

CountIf[x < 3, {1, 2, 3, 4, 5}]
gives you the number 2. 
CountIf[x < 3, A1:A10]
, where A1:A10 is a range of cells in the spreadsheet, counts all cells whose values are less than 3.

 Note: For list of numbers arbitrary condition may be used. For list of other objects one can use only conditions of the form
x==constant
orx!=constant
.
 CountIf[ <Condition>, <Variable>, <List> ]
 As above, using a more flexible syntax.
 Example:Given points P, Q, R
CountIf[x(A) < 3, A, {P, Q, R}]
will count only the points whose xcoordinate is less than 3. The variable A is replaced in turn with P then Q then R for the check. ThereforeCountIf[x(A) < 3, A, {(0, 1), (4, 2), (2, 2)}]
yields the number 2.