Viewing the result

One of the goals of EDF+ is maintaining back-compatibility with EDF. We are going to check the file with an script developed as an example to read EDF files. It is described in a tutorial on Scilab in Neurotraces. To run the script you have to install Scilab and exec the script loadedf.sce. The script can be downloaded here. Once executed, you follow the following steps

Select a record to begin with 1-5-->1
 initrectoread  =
 
    1.  
 str  =
 
 Select a record to end with 1-5   
Warning :redefining function: message                 
 
Select a record to end with 1-5-->5
 
-->patientid
 patientid  =
 
 X X X X                                                                
 
-->recordid
 recordid  =
 
 Startdate 01-JAN-2003 X X X                                            
  
 
-->duration
 duration  =
 
    1.  
  
-->label
 label  =
 
!Sin wave          !
!                  !
!EDF Annotations   !
 
-->nsamples
 nsamples  =
 
!   100. !
!   50.  !

We can see that the new EDF+ file is recognized as if it were an EDF file. The same result would have been got with other viewers. Now, we can explore the signal

-->plot(signals(1))

The result can be seen in figure 7.1

Figure 7.1: Plotting the five data records of wav.edf

We can see the original sin wave as a continuous record. Notice that we use a range of 200 (-100 to 100). We could increase the resolution in voltage by adjusting the physical and digital maximum and minimum. The normative document includes this very useful suggestion:

 Apply suitable scaling factors in such a way that a large part
 of the available range of -32768 till 32767 for the values of
 the analysis results is used.

For the sake of simplicity, we use a range from -100 to 100. A range from -30000 to 30000 would have given a much better amplitude resolution.

To see the annotations we will use yudit once more. After some arrangements, we are able to find the annotations and try to find the annotation including the unicode character 5927. The result can be seen in figure 7.2

Figure 7.2: Checking UTF-8 encoding

We can see the glyph of the Unicode 5927. Let's read the explanation given by Cheng Chung Hing about this character in his book Learning the characters through illustrations (Hai Feng Publishing Co 1999):

"From oracle bones we can see that it looked like the frontal view of a man
who is stretching his arms and legs to the limit in order to demonstrate
his breadth. The character means great and broad"

I choose this character to illustrate the beauty of the Chinese characters and how they can be included in annotations. I included the glyph as an illustration of the section of Neurotraces dedicated to EDF. An EDF+ viewer would be able to handle these annotations, allowing the inclusion of local expressions of very different cultures in the same frame.