.TH WFDB2MAT 1 "8 December 2013" "WFDB 10.5.22" "WFDB Applications Guide"
.SH NAME
wfdb2mat \- convert WFDB-compatible signal file to Matlab .mat file
.SH SYNOPSIS
\fBwfdb2mat -r\fR \fIrecord\fR [ \fIoptions\fR ... ]
.SH DESCRIPTION
.PP
This program converts the signals of any PhysioBank record (or one in
any compatible format) into a \fIrecord\fB.mat\fR file that can be
read directly using any version of Matlab, and a short
\fIrecord\fB.hea\fR text file containing information about the signals
(names, gains, baselines, units, sampling frequency, and start
time/date if known). In addition, \fBwfdb2mat\fR writes a brief
summary of this information to the standard output.
.PP
The \fB.mat\fR and \fB.hea\fR output files can also be read by
any WFDB application as record \fIRECm\fR.
.PP
This program does not convert annotation files; for that task,
\fBrdann\fR(1) is recommended.
.PP
The output \fB.mat\fR file contains a single matrix named \fBval\fR,
containing raw (unshifted, unscaled) samples from the selected \fIrecord\fR.
Using various options (below), one can select any time interval within a
record, or any subset of the signals, which can be rearranged as
desired within the rows of the matrix. Since \fB.mat\fR files are written
in column-major order (i.e., all of column \fIn\fR precedes all of column
\fIn+1\fR), each vector of samples is written as a column rather than as a
row, so that the column number in the \fB.mat\fR file equals the sample
number in the input record. If this seems odd, transpose your matrix
after reading it!
.PP
This program writes version 4 MAT-file format output files (see
http://www.mathworks.com/access/helpdesk/help/pdf_doc/matlab/matfile_format.pdf
for details).
The samples are written as 32-bit signed integers in little-endian format
if the record contains any format 24 or format 32 signals, as 8-bit unsigned
integers if the record contains only 8-bit unsigned samples, or as 16-bit
signed integers in little-endian format otherwise.
Although version 5 and newer versions of Matlab normally use a different (less
compact and more complex) format, they can read these files without difficulty.
The advantage of version 4 MAT-file format, apart from compactness and
portability, is that files in these formats are still WFDB-compatible, given
the \fB.hea\fR file constructed by this program.
.PP
Options for \fBwfdb2mat\fR include:
.TP
\fB-f\fR \fItime\fR
Begin at the specified \fItime\fR. By default, \fBwfdb2mat\fR starts at the
beginning of the record.
.TP
\fB-h\fR
Print a brief usage summary.
.TP
\fB-H\fR
Read the signal files in high-resolution mode (default: standard mode).
These modes are identical for ordinary records. For multifrequency records,
the standard decimation of oversampled signals to the frame rate is suppressed
in high-resolution mode (rather, all other signals are resampled at the highest
sampling frequency).
.TP
\fB-l\fR \fIinterval\fR
Limit the amount of output to the specified time \fIinterval\fR (in standard
time format; default: no limit). If both \fB-l\fR and \fB-t\fR are used,
\fBwfdb2mat\fR stops at the earlier of the two limits.
.TP
\fB-s\fR \fIsignal-list\fR
Convert only the signals named in the \fIsignal-list\fR (one or more
input signal numbers or names, separated by spaces; default: print all
signals). This option may be used to re-order or duplicate signals.
.TP
\fB-S\fR \fIsignal\fR
Search for the first valid sample of the specified \fIsignal\fR (a signal name
or number) at or following the time specified with \fB-f\fR (or the beginning of
the record if the \fB-f\fR option is not present), and begin converting at that
time.
.TP
\fB-t\fR \fItime\fR
Stop at the specified \fItime\fR. By default, \fBwfdb2mat\fR stops at the end
of the record.
.SS Example
.PP
To convert record \fBmitdb/200\fR, use this command:
.br
\fBwfdb2mat -r mitdb/200\fR
.PP
This works even if the input files have not been downloaded; in this case,
\fBwfdb2mat\fR reads them directly from the PhysioNet server.
.PP
The output files are \fBmitdb/200m.mat\fR and \fBmitdb/200m.hea\fR. Note that
if a subdirectory of the current directory named \fBmitdb\fR did not exist
already, it would be created by \fBwfdb2mat\fR. In addition, if the standard
output of \fBwfdb2mat\fR has been saved in a file named \fBmitdb/200m.info\fR,
then the converted data can be read and plotted in Matlab or Octave from within
the \fBmitdb\fR directory by running the command:
.br
\fBplotATM('200m.mat', '200m.info')\fR
.br
(Download \fBhttp://physionet.org/physiotools/matlab/plotATM.m\fR and install
it in your Matlab or Octave environment first.)
.PP
Note that when EDF (or EDF+, BDF, or BDF+) files are used as input, they may
have empty 'physical dimension' (units) fields, which imply that the associated
signals are dimensionless (for example, they may be event markers or categorical
variables). In such cases, \fBwfdb2mat\fR records the signal units as \fBnd\fR
(no dimension).
.SH ENVIRONMENT
.PP
It may be necessary to set and export the shell variable \fBWFDB\fR (see
\fBsetwfdb\fR(1)).
.SH AVAILABILITY
This program is provided in the \fIconvert\fR directory of the WFDB Software
Package. Run \fBmake\fR in that directory to compile and install it if it
has not been installed already.
.PP
The PhysioNet ATM (http://physionet.org/cgi-bin/ATM) provides web access to
\fBwfdb2mat\fR (select \fBExport signals as .mat\fR from the Toolbox).
.SH SEE ALSO
\fBa2m\fR(1), \fBedf2mit\fR, \fBsnip\fR(1), \fBwav2mit\fR(1), \fBxform\fR(1),
\fBwfdb\fR(3), \fBheader\fR(5)
.br
\fBhttp://physionet.org/physiotools/matlab/plotATM.m\fR
.SH AUTHOR
George B. Moody (george@mit.edu)
.SH SOURCES
http://www.physionet.org/physiotools/wfdb/convert/wfdb2mat.c