ECG Database Applications Guide
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wrsamp - write DB signal files
wrsamp [ options ... ] column [
column ... ]
wrsamp reads text-format input and writes the specified
columns in DB signal file format 16 (see signal(5)
), either to the standard
output or to a disk file (see the -o option below).
Normally, wrsamp's input
is line- and column-oriented, with line separator characters (usually ASCII
linefeeds) separating input lines, and field separator characters (usually
spaces or tabs) separating columns within each line. Columns need not
be of constant width; the only requirement is that one or more field separator
characters appear between adjacent columns. The output of rdsamp(1)
is
an example of an acceptable input format.
Lines are identified by line
number. The first line of input is line 0. Similarly, columns are identified
by column number, and the leftmost column is column 0. Columns may be
selected in any order, and any given column may be selected more than
once, or omitted. The order of column arguments determines the order of
the signals in the output (data from the first column specified are written
as signal 0, etc.) If an entry in a specified column is missing or improperly
formatted, wrsamp produces a warning message identifying the line and
column numbers, and inserts a zero in the output in place of the missing
or improperly formatted sample.
Options include:
- -c
- Check that each input
line contains the same number of fields. (This test is normally disabled,
to allow for input files containing preambles, trailers, or occasional
extra fields not intended to be read as samples.)
- -f n
- Start copying with
line n. By default, wrsamp starts at the beginning of its standard input
(line 0).
- -F n
- Specify the sampling frequency (in samples per second per
signal) for the output signals (default: 250). This option is useful only
in conjunction with -o, since it affects the output header file only. This
option has no effect on the output signal file, which contains one sample
per signal for each line of input. If you wish to change the sampling
frequency in the signal file, see xform(1)
.
- -G n
- Specify the gain (in A/D
units per millivolt) for the output signals (default: 200). This option
is useful only in conjunction with -o, since it affects the output header
file only. This option has no effect on the output signal file. If you
wish to rescale samples in the signal file, use -x.
- -h
- Print a usage summary.
- -i file
- Read input from the specified file (default: standard input).
- -l
n
- Read up to n characters in each line (default: 1024). Longer lines are
truncated (with a warning message identifying the line number of the offending
line).
- -o record
- Write the signal file in the current directory as record.dat,
and create a header file in the current directory for the specified record.
By default, wrsamp writes the signal file to its standard output in format
16 (see signal(5)
), and does not create a header file.
- -r c
- Interpret c
as the input line separator (default: \n, the ASCII linefeed character).
This option may be useful, for example, to read Macintosh files containing
carriage-return delimited lines. Note that no special treatment is required
for files containing both carriage returns and linefeeds.
- -s c
- Interpret
c as the input field separator (default: both spaces and tabs are treated
as input field separators). If this option is used, c is the only character
treated as a field separator.
- -t n
- Stop copying at line n (line n is not
processed). By default, wrsamp stops when it reaches the end of file on
its standard input.
- -x n
- Multiply all input samples by n (default: 1) before
writing them to the output signal file.
The shell variable DB should be
set and exported (see setdb(1)
).
rdsamp -r 100s | wrsamp -o 100w -F
360 1 2
This command creates a record named `100w' that is a copy of record
`100s' (although the signal file format is different). If the -F 360 option
were omitted, the output signal file (`100w.dat') would be unchanged, but
the header file for record `100w' would indicate that the sampling frequency
was (the default) 250 Hz, rather than 360 Hz as in record 100s; this is
because wrsamp has no other way of determining the sampling frequency
of its input. Note that columns 1 and 2 of wrsamp's input correspond to
signals 0 and 1 respectively; column 0 is the sample number, not useful
to wrsamp.
rdsamp(1)
, setdb(1)
, xform(1)
, signal(5)
This
program is included in version 8.1 and later versions of the DB Software
Package.
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