Scilab Home page | Wiki | Bug tracker | Forge | Mailing list archives | ATOMS | File exchange
Change language to: Français - Português - 日本語 - Русский

See the recommended documentation of this function

Scilab Help >> Scilab > Scilab keywords > power

# power

(^,.^) power operation

```t=A^b
t=A**b
t=A.^b```

### Arguments

A,t

scalar, polynomial or rational matrix.

b

a scalar, a vector or a scalar matrix.

### Description

• If `A` is a square matrix and `b` is a scalar then `A^b` is the matrix `A` to the power `b`.

• If `b` is a scalar and `A` a matrix then `A.^b` is the matrix formed by the element of `A` to the power `b` (element-wise power). If `A` is a vector and `b` is a scalar then `A^b` and `A.^b` performs the same operation (i.e. element-wise power).

• If `A` is a scalar and `b` is a matrix (or vector) `A^b` and `A.^b` are the matrices (or vectors) formed by `a^(b(i,j))`.

• If `A` and `b` are vectors (matrices) of the same size `A.^b` is the `A(i)^b(i)` vector (`A(i,j)^b(i,j)` matrix). Notes:

1. For square matrices `A^p` is computed through successive matrices multiplications if `p` is a positive integer, and by diagonalization if not (see "note 2 and 3" below for details).

2. If `A` is a square and Hermitian matrix and `p` is a non-integer scalar, `A^p` is computed as:

`A^p = u*diag(diag(s).^p)*u'` (For real matrix `A`, only the real part of the answer is taken into account).

`u` and `s` are determined by `[u,s] = schur(A)` .

3. If `A` is not a Hermitian matrix and `p` is a non-integer scalar, `A^p` is computed as:

`A^p = v*diag(diag(d).^p)*inv(v)` (For real matrix `A`, only the real part of the answer is taken into account).

`d` and `v` are determined by `[d,v] = bdiag(A+0*%i)` .

4. If `A` and `p` are real or complex numbers, `A^p` is the principal value determined by:

`A^p = exp(p*log(A))` (or `A^p = exp(p*(log(abs(A))+ %i*atan(imag(A)/real(A))))` ).

5. If `A` is a square matrix and `p` is a real or complex number, `A.^p` is the principal value computed as:

`A.^p = exp(p*log(A))` (same as case 4 above).

6. `**` and `^` operators are synonyms.

### Examples

```A=[1 2;3 4];
A^2.5,
A.^2.5
(1:10)^2
(1:10).^2

A^%i
A.^%i
exp(%i*log(A))

s=poly(0,'s')
s^(1:10)```