▁both ▁cases , ▁only ▁the ▁window ▁function ▁itself ▁will ▁have ▁real - valu ed ▁D T FT ▁samples . ▁ ▁Window ed ▁data ▁will ▁generally ▁lack ▁the ▁symmetry ▁to ▁preserve ▁that ▁characteristic . ▁ ▁But ▁other ▁than ▁the ▁predict able ▁sign ▁revers als , ▁the ▁phase ▁component ▁of ▁the ▁D T FT ▁will ▁be ▁representative ▁of ▁the ▁data , ▁not ▁the ▁window ▁function . ▁ ▁Tr unc ation ▁affect s ▁only ▁the ▁real ▁components ▁of ▁the ▁D T FT ▁samples . ▁ ▁The ▁imag inary ▁ones ▁remain ▁zero - valu ed . ▁ ▁Harris ▁attributes ▁this ▁effect ▁to ▁what ▁he ▁calls ▁D FT - even ▁symmetry . ▁ ▁Figure ▁Sam pling ▁the ▁D T FT ▁is ▁an ▁ex agger ated ▁example ▁of ▁both ▁methods , ▁also ▁showing ▁how ▁real - valu ed ▁samples ▁are ▁obtained ▁from ▁the ▁complex ▁D T FT . ▁ ▁The ▁effect ▁of ▁trunc ation ▁on ▁spectral ▁leak age ▁is ▁best ▁understood ▁in ▁terms ▁of ▁the ▁magnitude ▁of ▁the ▁D T FT , ▁shown ▁in ▁de ci b els . ▁ ▁At ▁figure ▁Gaussian ▁windows , ▁the ▁graph ▁l abeled ▁D T FT ▁periodic 8 ▁is ▁the ▁D T FT ▁of ▁the ▁trunc ated ▁window ▁l abeled ▁periodic ▁D FT - even ▁( both ▁blue ). ▁ ▁The ▁green ▁graph ▁l abeled ▁D T FT ▁symmetric 9 ▁corresponds ▁to ▁the ▁same ▁window ▁with ▁its ▁symmetry ▁restored . ▁ ▁The ▁D T FT ▁samples , ▁l abeled ▁D FT 8 ▁periodic ▁summ ation , ▁are ▁an ▁example ▁of ▁using ▁periodic ▁summ