power - Element-wise power - MATLAB (original) (raw)

Syntax

Description

C = [A](#btx%5F7d7-A).^[B](#btx%5F7d7-A) raises each element of A to the corresponding powers inB. The sizes of A andB 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.

example

C = power([A](#btx%5F7d7-A),[B](#btx%5F7d7-A)) is an alternate way to execute A.^B, but is rarely used. It enables operator overloading for classes.

Examples

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Create a vector, A, and square each 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).

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

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

a=[a1 a2], b=[b1b2b3], a .ˆ b=[a1b1a2b1a1b2a2b2a1b3a2b3].

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

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

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

Use the nthroot function to obtain the real roots.

Since R2023a

Create two tables and raise the first table to the power of the second. The row names (if present in both) and variable names must be the same, but do not need to be in the same orders. Rows and variables of the output are in the same orders as the first input.

A = table([1;2],[3;4],VariableNames=["V1","V2"],RowNames=["R1","R2"])

A=2×2 table V1 V2 __ __

R1    1     3 
R2    2     4

B = table([4;2],[3;1],VariableNames=["V2","V1"],RowNames=["R2","R1"])

B=2×2 table V2 V1 __ __

R2    4     3 
R1    2     1

C=2×2 table V1 V2 __ ___

R1    1       9
R2    8     256

Input Arguments

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Operands, specified as scalars, vectors, matrices, multidimensional arrays, tables, or timetables. 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 or1-by-N row vector). For more information, see Compatible Array Sizes for Basic Operations.

Operands with an integer data type cannot be complex.

Inputs that are tables or timetables must meet the following conditions: (since R2023a)

If an input is a table or timetable, then all its variables must have data types that support the operation.
If only one input is a table or timetable, then the other input must be a numeric or logical array.
If both inputs are tables or timetables, then:
- Both inputs must have the same size, or one of them must be a one-row table.
- Both inputs must have variables with the same names. However, the variables in each input can be in a different order.
- If both inputs are tables and they both have row names, then their row names must be the same. However, the row names in each input can be in a different order.
- If both inputs are timetables, then their row times must be the same. However, the row times in each input can be in a different order.

More About

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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

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

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.

Usage notes and limitations:

When both X and Y are real, butpower(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, butX .^ Y is complex, simulation produces an error and generated code returns NaN. To get the complex result, make the input value X complex by usingcomplex(X). For example,complex(X).^Y.
Code generation does not support sparse matrix inputs for this function.

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

The power function supports GPU array input with these usage notes and limitations:

If base A or exponent B are sparse,B must be a scalar.

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

Version History

Introduced before R2006a

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The power operator supports operations directly on tables and timetables without indexing to access their variables. All variables must have data types that support the operation. For more information, see Direct Calculations on Tables and Timetables.

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.