Diagnostic daytime multiple sleep latency test (MSLT) is used to diagnose narcolepsy and to measure the degree of daytime sleepiness. It measures how quickly you fall asleep in quiet situations during the day. It also monitors how quickly and how often you enter REM sleep.
Array formulas provide a way by which Excel users can discover such useful information. To explain the power of array formulas I'll use this database. It shows sales by Seller, Product, Region, and Customer, with Quantity and Total Sales, in dollars. I named each column of data with the label shown in row 1.
This is the normal behavior of Excel's own array functions. For example, if you array enter =ROW(A1:A3) into cells B1:B5, the result will be 1 2 3 #N/A #N/A. The ROW(A1:A3) returns an array with only three elements, so Excel fills in the rest of the calling range with #N/A values.