power, .^

Element-wise power

Syntax

C = A.^B

C = power(A,B)

Description

C = A.^B raises each element of A to the corresponding powers in B. The sizes of A and B must be the same or be compatible.

If the sizes of A and B are compatible, then the two arrays implicitly expand to match each other. For example, if one of A or B is a scalar, then the scalar is combined with each element of the other array. Also, vectors with different orientations (one row vector and one column vector) implicitly expand to form a matrix.

C = power(A,B) is an alternate way to execute A.^B, but is rarely used. It enables operator overloading for classes.

Examples

Square Each Element of Vector

Create a vector, A, and square each element.

A = 1:5;
C = A.^2

C = 1×5

     1     4     9    16    25

Find Inverse of Each Matrix Element

Create a matrix, A, and take the inverse of each element.

A = [1 2 3; 4 5 6; 7 8 9];
C = A.^-1

C = 3×3

    1.0000    0.5000    0.3333
    0.2500    0.2000    0.1667
    0.1429    0.1250    0.1111

An inversion of the elements is not equal to the inverse of the matrix, which is instead written A^-1 or inv(A).

Row Vector to Power of Column Vector

Create a 1-by-2 row vector and a 3-by-1 column vector and raise the row vector to the power of the column vector.

a = [2 3];
b = (1:3)';
a.^b

ans = 3×2

     2     3
     4     9
     8    27

The result is a 3-by-2 matrix, where each (i,j) element in the matrix is equal to a(j) .^ b(i):

$$\mathit{a}=\left[{\mathit{a}}_1{\mathit{a}}_2\right],\mathit{b}=\left[\begin{array}{c}{\mathit{b}}_1\\ {\mathit{b}}_2\\ {\mathit{b}}_3\end{array}\right],\mathit{a}.ˆ\mathit{b}=\left[\begin{array}{cc}{{\mathit{a}}_1}^{{\mathit{b}}_1}& {{\mathit{a}}_2}^{{\mathit{b}}_1}\\ {{\mathit{a}}_1}^{{\mathit{b}}_2}& {{\mathit{a}}_2}^{{\mathit{b}}_2}\\ {{\mathit{a}}_1}^{{\mathit{b}}_3}& {{\mathit{a}}_2}^{{\mathit{b}}_3}\end{array}\right].$$

Find Roots of Number

Calculate the roots of -1 to the 1/3 power.

A = -1;
B = 1/3;
C = A.^B

C = 0.5000 + 0.8660i

For negative base A and noninteger B, the power function returns complex results.

Use the nthroot function to obtain the real roots.

C = nthroot(A,3)

C = -1

Input Arguments

A, B — Operands

scalars | vectors | matrices | multidimensional arrays

Operands, specified as scalars, vectors, matrices, or multidimensional arrays. A and B must either be the same size or have sizes that are compatible (for example, A is an M-by-N matrix and B is a scalar or 1-by-N row vector). For more information, see Compatible Array Sizes for Basic Operations.

• Operands with an integer data type cannot be complex.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | logical | char
Complex Number Support: Yes

More About

IEEE Compliance

For real inputs, power has a few behaviors that differ from those recommended in the IEEE^®-754 Standard.

	MATLAB®	IEEE
power(1,NaN)	NaN	1
power(NaN,0)	NaN	1

Extended Capabilities

Tall Arrays

Calculate with arrays that have more rows than fit in memory.

This function fully supports tall arrays. For more information, see Tall Arrays.

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

• When both X and Y are real, but power(X,Y) is complex, simulation produces an error and generated code returns NaN. To get the complex result, make the input value X complex by passing in complex(X). For example, power(complex(X),Y).

• When both X and Y are real, but X .^ Y is complex, simulation produces an error and generated code returns NaN. To get the complex result, make the input value X complex by using complex(X). For example, complex(X).^Y.

• Code generation does not support sparse matrix inputs for this function.

GPU Code Generation

Generate CUDA® code for NVIDIA® GPUs using GPU Coder™.

Usage notes and limitations:

• When both X and Y are real, but power(X,Y) is complex, simulation produces an error and generated code returns NaN. To get the complex result, make the input value X complex by passing in complex(X). For example, power(complex(X),Y).

• When both X and Y are real, but X .^ Y is complex, simulation produces an error and generated code returns NaN. To get the complex result, make the input value X complex by using complex(X). For example, complex(X).^Y.

• Code generation does not support sparse matrix inputs for this function.

HDL Code Generation

Generate Verilog and VHDL code for FPGA and ASIC designs using HDL Coder™.

Both inputs must be scalar, and the exponent input, k, must be an integer.

Thread-Based Environment

Run code in the background using MATLAB® backgroundPool or accelerate code with Parallel Computing Toolbox™ ThreadPool.

This function fully supports thread-based environments. For more information, see Run MATLAB Functions in Thread-Based Environment.

GPU Arrays

Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™.

Usage notes and limitations:

• 64-bit integers are not supported.

For more information, see Run MATLAB Functions on a GPU (Parallel Computing Toolbox).

Distributed Arrays

Partition large arrays across the combined memory of your cluster using Parallel Computing Toolbox™.

This function fully supports distributed arrays. For more information, see Run MATLAB Functions with Distributed Arrays (Parallel Computing Toolbox).

Version History

Introduced before R2006a

R2016b: Implicit expansion change affects arguments for operators

Behavior changed in R2016b

Starting in R2016b with the addition of implicit expansion, some combinations of arguments for basic operations that previously returned errors now produce results. For example, you previously could not add a row and a column vector, but those operands are now valid for addition. In other words, an expression like [1 2] + [1; 2] previously returned a size mismatch error, but now it executes.

If your code uses element-wise operators and relies on the errors that MATLAB previously returned for mismatched sizes, particularly within a try/catch block, then your code might no longer catch those errors.

For more information on the required input sizes for basic array operations, see Compatible Array Sizes for Basic Operations.