MATLAB: Raising a negative value to a fraction power

power operation

I am rasing a negative value to a fraction power. Depending on how I write the operation (putting the negative value in parenthesis or not), the answer changes (see below)? Am I missing something?

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Exponentiation has a higher priority than negation, so -2^1.2 is -(2^1.2), this results in a negative real. On the other had (-2)^1.2 raises a negative number to a fractional power, because parentheses take priority over exponentiation, and the result is a complex number.

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MATLAB: Raising negative number to a power

Just put your negative values in brackets:

(-1.5)^2 = 2.2500

In your case Matlab is applying the sign afterwards, as it sees it as a standard operator and is following the usual operation order by calculating the power before subtraction.

MATLAB: Do unary operators like (+) and (-) used in conjunction with numbers not have precedence over the (^) operators while parsing at the MATLAB® command prompt

The documentation states:

Precedence levels determine the order in which MATLAB evaluates an expression. Within each precedence level, operators have equal precedence and are evaluated from left to right.

MATLAB uses the standard order of operations. The precedence rules for MATLAB are listed below, ordered from highest to lowest precedence level.

1) Parentheses ()

2) Transpose (.'), power (.^), complex conjugate transpose ('), matrix power (^)

3) Unary plus (+), unary minus (-), logical negation (~)

4) Multiplication (.*), right division (./), left division (.\), matrix multiplication (*), matrix right division (/), matrix left division (\)

5) Addition (+), subtraction (-)

6) Colon operator (:)

7) Less than (<), less than or equal to (<=), greater than (>), greater than or equal to (>=), equal to (==), not equal to (~=)

8) Element-wise AND (&)

9) Element-wise OR (|)

10) Short-circuit AND (&&)

11) Short-circuit OR ()

While performing parsing at the MATLAB command prompt, operators are given preference over the number. It should also be noted that for single unary operators like (+) or (-) to have precedence over a (^), they should be enclosed in parenthesis ().

For example:

(-2)^2

would give precedence to the (-) operator yielding the following output:

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MATLAB: Raising negative number to a power

MATLAB: Do unary operators like (+) and (-) used in conjunction with numbers not have precedence over the (^) operators while parsing at the MATLAB® command prompt

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