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See the recommended documentation of this function
isnan
check for "Not a Number" entries
Syntax
r=isnan(x)
Arguments
- x
real or complex vector or matrix r : boolean vector or matrix
Description
isnan(x)
returns a boolean vector or matrix which
contains true entries corresponding with "Not a Number"
x
entries and false entries corresponding with regular
x
entries.
In this paragraph, we give the reason of the existence of this function.
Consider the floating point number x
and assume that
we want to know if this number is a Not A Number.
The condition (x==%nan)
is false if x
is equal
to %nan
. This is why the function isnan
is helpful: it allows to
see if a floating point number is a NaN, without actually comparing its value
against %nan
.
Examples
isnan([1 0.01 -%nan %inf-%inf])
In the following example, we see that %nan
has very particular
comparison properties and compare the result with the isnan
function.
%nan == %nan %nan <> %nan isnan(%nan)
In the following example, we extract the non-NaNs values y
from the array x
.
x = [1 2 %nan 3 %nan 4] k = find(~isnan(x)) y = x(k)
See also
- isinf — tests for infinite elements
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