NMRPipe Processing Functions
EM: Exponential Multiply Window.

EM applies an exponential window. The exponential is
specified in terms of a Lorentzian line broadening (lb) in Hz.
In the following formula, tSize
is the number of
timedomain points, which defines the length of the window
function; EM[i] is the EM window function from i = 0
(first point) to i = tSize  1
(last point);
sw
is the sweep width in Hz.
EM[i] = exp( PI*i*lb/sw )
In addition to functionspecific options, the EM window function provides the following features common to all NMRPipe window functions:
EM OPTIONS
lb lbHz
(Q1) Specifies the exponential decay of the window in
terms of a line broadening in Hz. Negative values will
generate an increasing exponential window, which
corresponds to a line sharpening. The linebroadening
parameter is often selected to match the natural
linewidth.
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
(here, Q1) 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.
HEADER VALUES
EM 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,
NDAPODQ3, and NDC1.
The header values NDAPODCODE, NDAPODQ1, NDAPODQ2, NDAPODQ3,
and NDC1 are updated according to the values applied during
processing.