Teledyne LeCroy WaveExpert 100H Operators Manual - Manual (Page 127)

Wave Expert
WE-OM-E Rev A
125
pctl Percentile
Definition: Computes the horizontal data value that separates the data in a histogram
such that the population on the left is a specified percentage `xx' of the total
population. When the threshold is set to 50%, pctl is the same as hmedian.
Description: The total population of the histogram is determined. Scanning from left to
right, the population of each bin is summed until a bin that causes the sum to
equal or exceed `xx'% of the population value is encountered. A ratio of the
number of counts needed for `xx'% population/total bin population is then
determined for the bin. The horizontal value of the bin at that ratio point of its
range is found, and returned as pctl.
Example: The total population of a histogram is 100. The histogram range is divided into
20 bins and `xx' is set to 25%. The population sum at the sixth bin from the left
is 22. The population of the seventh is 9 and its sub-range is 6.1 to 6.4 V. The
ratio of counts needed for 25% population to total bin population is:
3 counts needed / 9 counts = 1/3.
The value for pctl is:
6.1 volts + .33 * (6.4 - 6.1) volts = 6.2 volts.