# isinf

tests for infinite elements

### Syntax

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

`%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

### See also

- percentinf — infinity
- isnan — check for "Not a Number" entries
- isreal — check if a variable is stored as a complex matrix
- isnum — tests if a string represents a number
- type — returns the type of a Scilab object

### History

Version | Description |

6.1.0 | Extension to polynomials. |

Report an issue | ||

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