Not-a-Number.
NaN
NaN is the IEEE arithmetic representation for Not-a-Number (NaN). NaNs result from operations which have undefined numerical results.
The following operations produce NaN:
Any arithmetic operation on a NaN, such as sqrt(NaN)
Addition or subtraction, such as magnitude subtraction of infinities as (+Inf)+(-Inf)
Multiplication, such as 0*Inf
Division, such as 0/0 and Inf/Inf
Remainder, such as rem(x,y) where y is zero or x is infinity
Comparison by way of predicates involving < or >, such as min([Inf NaN]) and max([Inf NaN])
Logical operations involving NaNs always return false, except ~= (not equal). Consequently, the statement NaN ~= NaN is true while the statement NaN == NaN is false.
dbstop, finite, Inf, isinf, isnan
(c) Copyright 1994 by The MathWorks, Inc.