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isinf

tests for infinite elements

r = isinf(x)

Arguments

x

matrix of real or complex numbers, or of polynomials with real or complex coefficients.

r

matrix of booleans of the same size as x.

Description

x are real or complex numbers: r = isinf(x) returns the matrix r of booleans such that r(i) is %T if abs(x(i)) is infinite, and %F otherwise.

x are polynomials with real or complex coefficients: Then after r = isinf(x), r(i) is %T if at least one of the x(i) coefficients is infinite, and %F otherwise.

Examples

With real and complex numbers:

[i, inf, nan] = (%i, %inf, %nan);
isinf([-1  0.01 -inf  inf  nan])
isinf([2+i, -10-inf, inf+i])
isinf([nan-i, nan+i*inf])
isinf(inf-nan*i)
--> isinf([-1  0.01 -inf  inf  nan])
ans  =
F F T T F

--> isinf([2+i, -10-inf, inf+i])
ans  =
F T T

--> isinf([nan-i, nan+i*inf])
ans  =
F T

--> isinf(inf-nan*i)
ans  =
F
Please note that %inf-%nan*%i is computed as %inf - %nan*complex(0,1) == %inf - complex(%nan*0, %nan*1) == %inf - complex(%nan, %nan) == complex(%inf-%nan, -%nan) == complex(%nan, %nan) , where Inf is eaten by Nan and no longer appears.

With polynomials :

p = poly([%nan -2 0 3],"x","coeff")
q = poly([0 %inf %i],"x","coeff")
r = poly([%nan %inf*%i 1],"x","coeff")
isinf([p q r])
--> p = poly([%nan -2 0 3],"x","coeff")
p  =
Nan -2x +3x³

--> q = poly([0 %inf %i],"x","coeff")
q  =
Infx +ix²

--> r = poly([%nan %inf*%i 1],"x","coeff")
r  =
Nan -(Nan-Infi)x +x²

--> isinf([p q r])
ans  =
F T F

• percentinf — 無限大
• isnan — "Not a Number" エントリを調べる
• isreal — 変数が実数または複素数のエントリかどうかを調べるc
• isnum — 文字列が数字であるかどうかを調べる
• type — 変数の型を返す

History

 バージョン 記述 6.1.0 Extension to polynomials.