3. The computer-readable storage medium of claim 2 , wherein the process derives the absence length sequence from the presence sequence by using an algorithm with the following steps: Step 1: divide a collection period into fixed length time intervals with at least one observed data point within each interval, and number the time intervals; Step 2: for each time interval with at least one direct observation, store a zero in the corresponding absence length field at that time interval, otherwise store a non-zero value; Step 3: select all the data points that have initial absence length not zero, ordered by time interval along with their corresponding row numbers which are an increasing consecutive number sequence; Step 4: subtract the row number for each data point selected in step 3 from its corresponding time interval and assign to a variable, denoted a grouptag; Step 5: group the data points in step 4 by their grouptag; Step 6: select the count for each group as the absence length value for each data point that is a member of that group; Step 7: update the absence length values.
2. The computer-readable storage medium of claim 1 , wherein the converting step comprises: computationally with at least one processor operating with the memory generating an interval performance data presence sequence from the interval sequence, said generated sequence denoted as a “presence sequence” herein, each interval sequence null value corresponding to a zero in the presence sequence and each interval sequence non-null value corresponding to a one in the presence sequence; and computationally with at least one processor operating with the memory deriving the absence length sequence from the presence sequence.