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Why y is a complx number? y = x.^(2/3)

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isku
isku 2013-4-14
x = -10:1:10
y = x.^(2/3)
Actually I try to plot y = x^(2/3)but I get warning from Matlab.
I try fplot(x^(2/3)[-10,10])

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Azzi Abdelmalek
Azzi Abdelmalek 2013-4-14
编辑：Azzi Abdelmalek 2013-4-14
use
y=abs(x.^(2/3))
You are calculating the roots of negative numbers, they are obviously complex
(-10)^(2/3) is ((-10)^(1/3))^2

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Walter Roberson
Walter Roberson 2013-4-15
编辑：Walter Roberson 2013-4-15
Remember, in MATLAB, (2/3) is 0.333333<etc>, a floating point number, rather than being the indicator of taking the square of the third root of the number.
In MATLAB, when you raise a value to a non-integer power, the result x^y is defined as exp( log(x) * y). When x is negative, log(x) is complex. Multiplying a complex number by a floating point number is going to give you a complex number. exp() of a complex number is usually a complex number.

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