NMRPipe Processing Functions
HT: Hilbert Transform
HT applies a Hilbert transform (HT) to the vectors in the data. Its usual purpose is to reconstruct the imaginary part of real-only frequency-domain data in cases where the imaginary part was deleted during processing. This in turn allows spectra to be re-phased or inverse-transformed whenever needed, even if imaginary data was previously deleted.
The result of an HT will be complex. If the input vectors already have an imaginary part, this part will be replaced by the HT.
In particular cases, the HT can reconstruct imaginary data exactly. The requirements for this are:
This option enables mirror-image HT mode, suitable for data which have a first order phase correction P1 = 180 (1/2 point acquisition delay). This option works by building a temporary mirror image of the original spectrum which has the same behavior as a spectrum with no acquisition delay.
This option forces the HT not to use mirror-image mode.
This option enables use of temporary zero-filling for speed. Zero-filling is disabled by default.
This option disables use of temporary zero-filling for speed. This is the default.
This option will attempt to automatically choose whether or not a mirror image HT is needed (only when the recorded P1 is 180 and data have not been extracted to a smaller region), and whether temporary zero-filling can be used (all other cases).
If this option is included, HT will update the header value NDAPOD recording the number of valid time-domain points.
The following is a typical recipe for inverse processing and reprocessing with LP for a given dimension:
| nmrPipe -fn HT -auto \ | nmrPipe -fn PS -inv -hdr \ | nmrPipe -fn FT -inv \ | nmrPipe -fn ZF -inv \ | nmrPipe -fn SP -inv -hdr \ | nmrPipe -fn LP -fb \ | nmrPipe -fn SP -hdr \ | nmrPipe -fn ZF -auto \ | nmrPipe -fn FT \ | nmrPipe -fn PS -hdr -di \The following scheme transforms a 2D spectrum back into a 2D hypercomplex FID:
nmrPipe -in test.ft2 \ | nmrPipe -fn TP \ | nmrPipe -fn HT -auto -verb \ | nmrPipe -fn PS -inv -hdr \ | nmrPipe -fn FT -inv \ | nmrPipe -fn ZF -inv \ | nmrPipe -fn APOD -inv -hdr -ad \ | nmrPipe -fn TP -hyper \ | nmrPipe -fn HT -auto -verb \ | nmrPipe -fn PS -inv -hdr \ | nmrPipe -fn FT -inv \ | nmrPipe -fn ZF -inv \ | nmrPipe -fn APOD -inv -hdr \ -out test.fid -ov