home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
Business Shareware
/
Business Shareware.iso
/
start
/
gfxapps
/
techplt1
/
tpsht_03.hlp
< prev
next >
Wrap
Text File
|
1992-09-20
|
3KB
|
128 lines
** File: TPSht_03.hlp
** Index: 42
** More Sheet View Help
:: Filtering commands
:: Smoothing commands
█ Filtering
This menu contains commands that
perform digital filtering. These filters
are infinite impulse response (IIR)
filters.
█ Low-Pass
This command lets you perform low-pass
digital filtering. It displays the
Low-Pass Filter dialog box. In this
dialog box, you specify the cut-off
frequency F0. This filter only lets
signal components with frequency less
than F0 pass through.
█ Hi-Pass
This command lets you perform high-pass
digital filtering. It displays the
High-Pass Filter dialog box. In this
dialog box, you specify the cut-off
frequency F0. This filter only lets
signal components with frequency greater
than F0 pass through.
█ Band-Pass
This command lets you perform band-pass
digital filtering. It displays the
Band-Pass Filter dialog box. In this
dialog box, you specify the lower cut-off
frequency F0 and upper cut-off frequency
F1. This filter only lets signal
components with frequency between F0 and
F1 pass through.
█ Notch
This command lets you perform Notch
digital filtering. It displays the
Notch Filter dialog box. In this dialog
box, you specify the fiducial frequency
F0 and the notch width e0. This filter
removes only a narrow frequency band
around the fiducial frequency F0 with
bandwidth 2*e0.
█ Smoothing
This menu contains commands that
perform digital data smoothing. For
engineers and scientists, experimental
data often contain a large amount of
spurious noise. TechPlot implements
several commonly used smoothing techniques
for the purpose of removing noise from
observed data. Each of the commands in
this menu will display a dialog box. You
will need to specify the column you want
to smooth and window sizes (if any) in the
dialog box.
█ Lanczos
This method is due to Lanczos; it is a
fourth order smoothing of data points.
█ Averaging
This is the simplest type of filter; it
is also called the linear filter.
The following moving window methods
(left and right) are special cases of
this method. You specify both left and
right window sizes in the dialog box.
█ Moving Window (Left)
This method uses the same formula as
above. In this case, NR=0 and NL is the
window size. You specify the left
window size in the dialog box.
█ Moving Window (Right)
This method uses the same formula as
above. In this case, NL=0 and NR is the
window size. You specify the right
window size in the dialog box.
█ Savitzky-Golay
This smoothing routine is adapted from
Press et al [13]; it consists of fitting
a least squares fourth degree polynomial
through the data point and several points
on either side. The data point is
replaced by the value of the fitted
polynomial evaluated at the abscissa of
the data point. The left and right
window size is specified by user in the
dialog box.
█ Gram 1-3
This method uses Gram's first-degree
three-point formulas, as described in
Hildebrand's "Introduction to Numerical
Analysis", Chapter 7, to smooth a series
of equally spaced values.
█ Gram 3-5
This method is similar to Gram 1-3,
except that Gram's third-degree
five-point formulas are used.