19804 Maycrest Way
Germantown MD 20876 USA
301 8060867
delaglio@nmrscience.com
NMRPipe Processing Functions
GMB: Another Version of the Gauss Window.

GMB applies a Gausslike window, inspired by a similar window function found on Bruker spectrometers. It is somewhat similar to the GM function, and like this function, it also applies a combination of an exponential and a Gaussian.
In the following formula for GMB, tSize
is th number of
timedomain points, which defines the length of the window
function; GMB[i] is the window function from i = 0
(first
point) to i = tSize  1
(last point); and sw
is the sweep width in Hz.
Given the GMB adjustable parameters lb
and gb
:
GMB[i] = exp( a*t  b*t*t )where
t = i/sw aq = tSize/sw a = PI*lb b = a/(2.0*gb*aq)In addition to functionspecific options, the GMB window function provides the following features common to all NMRPipe window functions:
GMB OPTIONS
lb lbVal
(Q1) Specifies an exponential factor lb
,
as used in the
formula given above. This value is usually specified
as a negative number which is about the same size as
the natural linewidth in Hz. The default value is 0.0,
which means no exponential term will be applied.
gb gbVal
(Q2) Specifies a Gaussian factor gb
,
as used in the formula
given above. It is usually specified as a positive
number which is a fraction of 1.0. The default
value is 0.0, which leads to an undefined window function
according to the formula; for this reason, the
Gaussian term is omitted from the calculation
when gb 0.0
is given.
GENERIC WINDOW OPTIONS
size aSize
Specifies the number of points in the window function.
The default value is the valid timedomain size
recorded in the data header.
start aStart
Specifies the starting point of the window function.
The default value is 1, which means the window function
starts at the first point of the FID. This option is
intended for creation of composite windows by application
of different functions to different regions of the
FID.
c fScale
Specifies the scaling applied to the first point of the
FID, which influences the zeroorder offset in the
corresponding spectrum. The default value is 1.0,
which means no first point adjustment is applied. A
value of 0.5 is usually appropriate in cases where no
substantial firstorder phase correction will be
applied.
one
This flag influences the values used "outside" the window
function, in cases where the window size is smaller
than the actual number of data points. By default,
data values outside the window region are multiplied by
zero when the window is applied. However if the one
flag is used, data values outside the window region
will be multiplied by 1.0 when the window is applied.
This flag is intended to assist creation of composite
windows by application of different functions to different
regions of the FID.
hdr
When this flag is used, default window parameters
(Q1 and Q2) will be extracted from the data header,
along with the first point scaling (C1). This requires that
all of these parameters have already been recorded, for
instance during previous processing or format conversion
(see EXAMPLES below). Additional commandline can
be used to override values restored from the header.
The window parameters stored in the data header can be
viewed using the showhdr program, for example:
showhdr verb test.ft2
inv
When this flag is used, the inverse (1/window) of the
selected window and first point scale will be applied.
This option is intended for removing a
previouslyapplied window in inverse processing
schemes. This option should generally only be used on
window functions which have no values close or equal to
zero. In cases where the window does have a zero
value, the inverse window is also given as zero.
EXAMPLES
A typical usage of a GM and GMB window:
nmrPipe fn GM g1 20 g2 35 nmrPipe fn GMB lb 20 gb 0.25
HEADER VALUES
GMB and the other nmrPipe window functions use the recorded timedomain size (NDAPOD) to establish their default length.
When the hdr
flag is used, default window parameters are
extracted from header values NDAPODCODE, NDAPODQ1, NDAPODQ2,
and NDC1.
The header values NDAPODCODE, NDAPODQ1, NDAPODQ2, and NDC1 are updated according to the values applied during processing.