Calculate the FFT from Vec elements [VecIndex]..[VecIndex+Len-1] and store the results in the calling object elements [Index]..[Index+Len-1]. The Len parameter must be a power of two. Size and TMtxVec.Complex properties of the calling object must be set explicitly. An exception is raised if TMtxVecBase.ConditionCheckConditionCheckis True and array borders are overrun. If Vec is complex, then complex to complex forward FFT is performed. If Vec is real, then real to complex forward FFT is performed. 

This is the indexed version of the FFT routine TVec.FFT. Look there for more information on FFT parameters and storage requirements.

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