IPAP conversion and processing schemes can differ substantially
based on:

1. Whether the data are gradient enhanced.

2. Whether the IP/AP loop is the innermost one of the pulse sequence,
or the real/imaginary loop is the inner one.

Generally, the nmrPipe function "COADD" is used to select or combine
the IP/AP channels.

I find it helpful to process the IP and AP channels separately,
and then combine them after processing. This makes it possible
to inspect the data to choose a scaling factor that will lead
to the best IP/AP cancelation.

The stand-alone program "addNMR" can also be used to re-combine
processed IP or AP data.

Some examples are below.


Cheerful Regards,

big fd

-------------------------------------------------------------------------
If the IP/AP channel is in the innermost loop, the selection or
combination of AP/IP data should be done at the start of processing:

nmrPipe -in ./test.fid \
| nmrPipe -fn COADD -cList 1 -1.11 -axis Y -time \
| nmrPipe -fn SP -off 0.4 -end 0.98 -pow 2.0 -c 1.0 \
| nmrPipe -fn ZF -size 4096 \
| nmrPipe -fn FT -verb \
| nmrPipe -fn PS -p0 -80.0 -p1 -180.0 -di \
| nmrPipe -fn EXT -x1 10ppm -xn 6.0ppm -sw \
| nmrPipe -fn TP \
| nmrPipe -fn SP -off 0.4 -end 0.98 -pow 1.0 -c 1 \
| nmrPipe -fn ZF -size 4096 \
| nmrPipe -fn FT -verb \
| nmrPipe -fn PS -p0 -90 -p1 180.0 -di \
| nmrPipe -fn CS -rs -1ppm -neg -sw \
| nmrPipe -fn TP \
-ov -out A-B.DAT

-------------------------------------------------------------------------
If the IP/AP loop is outside the real/imaginary loop, the selection
of combination of AP/IP data should be done after the direct dimension
is processed.

Note that in this case, one IP/AP channel is 90 degrees out of phase
with respect to the other:

#!/bin/csh

var2pipe -in ./fid -noaswap \
-xN 1024 -yN 484 \
-xT 512 -yT 242 \
-xMODE Complex -yMODE Complex \
-xSW 6999.738 -ySW 2000.000 \
-xOBS 499.628 -yOBS 50.633 \
-xCAR 4.773 -yCAR 118.860 \
-xLAB HN -yLAB N \
-ndim 2 -aq2D States \
-out ./test.fid -verb -ov

nmrPipe -in test.fid \
| nmrPipe -fn SOL \
| nmrPipe -fn SP -off 0.5 -end 0.98 -pow 2 -c 0.5 \
| nmrPipe -fn ZF -auto \
| nmrPipe -fn FT \
| nmrPipe -fn PS -p0 177 -p1 0.0 -di \
| nmrPipe -fn EXT -left -sw -verb \
| nmrPipe -fn TP \
| nmrPipe -fn COADD -cList 1 0 -time \
| nmrPipe -fn SP -off 0.5 -end 0.98 -pow 1 -c 0.5 \
| nmrPipe -fn ZF -auto \
| nmrPipe -fn FT \
| nmrPipe -fn PS -p0 0 -p1 0 -di \
| nmrPipe -fn TP \
| nmrPipe -fn POLY -auto \
-verb -ov -out A.ft2

nmrPipe -in test.fid \
| nmrPipe -fn SOL \
| nmrPipe -fn SP -off 0.5 -end 0.98 -pow 2 -c 0.5 \
| nmrPipe -fn ZF -auto \
| nmrPipe -fn FT \
| nmrPipe -fn PS -p0 177 -p1 0.0 -di \
| nmrPipe -fn EXT -left -sw -verb \
| nmrPipe -fn TP \
| nmrPipe -fn COADD -cList 0 1 -time \
| nmrPipe -fn SP -off 0.5 -end 0.98 -pow 1 -c 0.5 \
| nmrPipe -fn ZF -auto \
| nmrPipe -fn FT \
| nmrPipe -fn PS -p0 -90 -p1 0 -di \
| nmrPipe -fn TP \
| nmrPipe -fn POLY -auto \
-verb -ov -out B.ft2

addNMR -in1 A.ft2 -in2 B.ft2 -out A+B.ft2 -c1 1.0 -c2 1.25 -add
addNMR -in1 A.ft2 -in2 B.ft2 -out A-B.ft2 -c1 1.0 -c2 1.25 -sub