Convert data from a matlab array into Physionet WFDB format file.
Input Paramater are:
X -(required) NxM matrix of M signals with N samples each. The
signals can be of type double.The signals are assumed to be
in physical units already and will be converted to
fname -(required) String where the the header (*.hea) and data (*.dat)
files will be saved (one single name for both, with no sufix).
Fs -(Optional) 1x1 sampling frequency in Hz (all signals must have
been sampled at the same frquency). Default is 1 Hz.
bit_res -(Optional) 1xM (or Mx1):scalar determining the bit depth of the conversion for
1x1 : If all the signals should have the same bit depth
Options are: 8, 16, and 32 ( all are signed types). 16 is the default.
adu -(Optional) Describes the physical units (default is 'mV').
Three input formats:
- String delimited by forward slashes (e.g. 'V/mV/mmHg'), with
M-1 slash characters
- Single string (e.g. 'V'), in which case all signals will
have the same physical units.
- Cell array of strings, where the total units entered has to equal M
(number of channels).
info -(Optional) String that will be added to the comment section of the header file.
For multi-lined comments, use a cell array of strings. Each
cell will be output on a new line. Note that comments in the
header file are automatically prefixed with a pound symbol (#)
gain -(Required for digital only) Scalar or Mx1 array of floats indicating the difference in sample values
that would be observed if a step of one physical unit occurred in the original
analog signal. If the 'isdigital' field is 1, this field is mandatory. Otherwise,
this field is ignored if present.
baseline -(Required for digital only) Mx1 array of integers that specifies the sample value for each channel
corresponding to 0 physical units. Not to be confused with 'ADC zero' which
is currently always taken and written as 0 in this function. If
the 'isdigital' field is 1, this field is mandatory. Otherwise,
this field is ignored if present.
sg_name -(Optional) Cell array of strings describing signal names.
isquant -(Optional) Logical value (default=0). Use this option if the
input signal is already quantitized and you want to remove round-off
error by mapping the original values to integers prior to fixed
point conversion. This field is only used for input physical
signals. If 'isdigital' is set to 1, this field is ignored.
isdigital -(Optional) Logical value (default=0). Specifies whether the input signal is
digital or physical (default). If it is digital, the signal values will be
directly written to the file without scaling. If the signal is physical,
the optimal gain and baseline will be calculated and used to digitize the signal
to write the WFDB file. This flag also decides the allowed
input combinations of the 'gain' and 'baseline' fields.
Digital signals must have both, and physical signals must have
neither (as the ideal values will be automatically calculated).
xbit -(Optional) NxM the quantitized signals that written to file (possible
rescaled if no gain was provided at input). Useful for comparing
and estimating quatitization error with the input double signal X
(see examples below).
NOTE: The signals can have different amplitudes, they will all be scaled to
a reference gain, with the scaling factor saved in the *.hea file.
Written by Ikaro Silva 2010
Modified by Louis Mayaud 2011, Alistair Johson 2016
See also wrsamp, wfdbdesc
%%%%%%%%% Example 1 %%%%%%%%%%%%
display('***This example will write a Ex1.dat and Ex1.hea file to your current directory!')
s=input('Hit "ctrl + c" to quit or "Enter" to continue!');
%Generate 3 different signals and convert them to signed 16 bit in WFDB format
clear all;clc;close all
%First signal a ramp with 2^16 unique levels and is set to (+-) 2^15 (Volts)
%Thus the header file should have one quant step equal to (2^15-(-2^15))/(2^16) V.
%Second signal is a sine wave with 2^8 unique levels and set to (+-) 1 (mV)
%Thus the header file should one quant step equal a (1--1)/(2^8) adu step
%Third signal is a random binary signal set to to (+-) 1 (V) with DC (to be discarded)
%Thus the header file should have one quant step equal a 1/(2^15) adu step.
sig3=(rand(N,1) > 0.97)*2 -1 + 2^16;
%Concatenate all signals and convert to WFDB format with default 16 bits (empty brackets)
sig=[sig1 sig2 sig3];
% %NOTE: If you have WFDB installed you can check the conversion by
% %uncomenting and this section and running (notice that all signals are scaled
% %to unit amplitude during conversion, with the header files keeping the gain info):
% !rdsamp -r Ex1 > foo
% plot(x(:,1),x(:,2));hold on;plot(x(:,1),x(:,3),'k');plot(x(:,1),x(:,4),'r')
%%%%%%% End of Example 1%%%%%%%%%