Mistake in fft() help (calculation of single-sided spectrum)?

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Steradiant
Steradiant 2019-10-11
回答： Samatha Aleti 2019-10-18
In the fft() help, a single sided spectrum is calculated as follows:
Y = fft(X);
P2 = abs(Y/L);
P1 = P2(1:L/2+1);
P1(2:end-1) = 2*P1(2:end-1);
First question: Regarding line 3. Why is the entry L/2+1 also taken into accout for the single sided spectrum? Shouldn't this value be part of the other side of the spectrum?
Second question: Regarding line 4. Why is the last entry not multiplied by 2 (the end value of the entry is end-1 instead of end)?

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Samatha Aleti
Samatha Aleti 2019-10-18

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