MATLAB extension

MATLAB extension (windows only)

If Matlab Version 5 (or above) is installed, Scream can automate the task of acquiring, selecting, converting, and processing data using a Matlab automation server.

Three conditions must be met before the Matlab interface operates:

Matlab 5 (or above) installed, with the signal processing toolbox
Matlab registered as an automation server
The file scrfft.m copied to the bin directory of Matlab.

scrfft.m is included in the Scream! distribution. It is a script file which Scream calls to execute the necessary Matlab commands to perform a Power Spectral Density plot. Users are free to modify this script file, but no support can be offered for modified files.

To select data and initiate an automated analysis, follow the steps:

display the required data stream in a WaveView window, adjusting time scaling for required time span.
When the desired amount of data is received, switch to pause mode, by pressing the Pause button in the WaveView window.
Select the exact data to be transferred by dragging the cursor over the data stream WHILST HOLDING THE SHIFT OR CTRL KEY. The readout in the top-left corner of the highlighted box indicates the number of samples that will be used by the supplied PSD script file for analysis.
When the mouse button is released, the selected samples will be saved to file. A pop-up menu will appear, and the "scrfft" option should be selected (see also Data Selection). A Matlab automation server will be started, and instructed to execute the scrfft.m script.

The samples are saved as ASCII in files in the standard ‘temp’ directory. By default, each stream is saved in a file called "samplesX.txt" where X is an incrementing number. In addition, a header file "scrhdr.txt" is saved with information about the data in the samplesX.txt files (start time, complete path and file name, sample rate, System ID and Stream ID).

Prior to executing scrfft, four variables are initialised. The first three variables are cell arrays, where each cell relates to a stream, in a multiple stream selection:

id- the streamID of the stream
Fs- the sample rate of the stream.
ifile- full specification of the data file.
t- the title for the figure - the Date/Time of the first sample

In the case where the SHIFT key was used to select the streams, the highlighted streams are transferred to the cell arrays from top to bottom. I.e. The top stream ID is matlab variable id{1}, the next id{2} and so on.

In the case where the CTRL key was used to select the streams, the first stream to be clicked on is the cell reference {1}, and the stream pointed to when the mouse cursor was released is cell reference {2}.

Although the default file names are samplesX.txt, other filename conventions can be specified by using the /m:filespec command line parameter at program start-up. filespec uses the same formatting codes as the filename convention.