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isnan

isnan(f) -> Bool

Test whether a floating point number is not a number (NaN)

Examples

1. Check if a floating-point number is NaN:

   julia> isnan(2.5)
   false
   
   julia> isnan(sqrt(-1))
   true

   In these examples, the isnan function is used to check if a given floating-point number is NaN. It returns true if the number is NaN and false otherwise.

2. Handle NaN values in an array:

   julia> arr = [1.0, 2.5, NaN, 4.2];
   julia> isnan.(arr)
   4-element BitArray{1}:
   false
   false
   true
   false

   Here, isnan. is used in conjunction with broadcasting (.) to check if each element of the array arr is NaN. It returns a boolean array indicating the presence of NaN values.

3. Filter out NaN values from an array:

   julia> arr = [1.0, 2.5, NaN, 4.2];
   julia> filter(!isnan, arr)
   3-element Array{Float64,1}:
   1.0
   2.5
   4.2

   In this example, the filter function is used along with the !isnan predicate to remove NaN values from the array arr. It returns a new array without the NaN elements.

Common mistake example:

julia> isnan("NaN")
ERROR: MethodError: no method matching isnan(::String)

In this example, the isnan function is mistakenly applied to a string instead of a floating-point number. Ensure that the input to isnan is a valid floating-point number to avoid such errors.

See Also

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