To find the median of a set of data, you need to arrange the values in ascending order and then find the middle value. If the number of values is odd, the median is the middle value. If the number of values is even, the median is the average of the two middle values.

Arranging the given data in ascending order: 0, 0, 1, 1, 2, 4, 4, 4, 4

There are 9 values, which is an odd number. The middle value is the fifth value, which is 2.