marker

Marker analysis mainly serves the purpose of extracting or generating timing information, that allows to process other data channels in defined subsets. All standard data analysis types check wether timing information is available for the processed file before loading the data and can thus make use of marker-based timing information. The mechanism used for timing in anslab is simple: when a data file is read, anslab looks for an m-file with the same name as the data file, in the folder where the data file is stored. If this m-file exists, it is evaluated as matlab-script. If after evaluation, a valid variable named 'T' exists, timing is based on this variable.

For instance, if for a data file

    F:\tex\raw\tex00101.acq

an m-file

  F:\tex\raw\tex00101.m

exists and it contains the following text:

    T = [...
    1    0    1800    1800;...
    2    1800    1903.519    103.519];

anslab will recognize 2 valid segment definitions. The first segment then begins at 0 seconds after file begin and ends at 1800 seconds after file begin, thus has a length of 1800 seconds. The second interval starts at 1800 and ends at 1903.519 seconds after file begin, spanning 103.519 seconds. 

The 'marker' analysis type allows you to generate this type of timing files automatically.

file naming

Timing files are named according to the raw datafile the are extracted from plus a customazible file extension. You can the default extension  <<  .m >>   to  <<   .spectral.m  >>  or <<    .icg.m >>   to create timing files for specific analysis types, but this is not mandatory. Renaming the files manually works just as well.

batch processing
Marker file extraction can most adequately be done in batchmode. However, to tell anslab which type of timing file to create, you must set the marker-options in the anslab options dialog according to your needs. Basically for every dialog question given in the non-batch analysis, there is a default option, that you can use to give your answer for all files in the batch. Thus, the number of marker channels, their type and name, the minimum and maximum event duration, events of interest and events to ignore are all taken from the default settings. Be sure also to select or deselect the 'ignore subsequent event with identical marker value if you wish to ignore or not repeated marker values.

IMPORTANT:
Marker channel analysis ist optimized for one well calibrated digital marker channel, that has a relatively small set of discrete values (0 to 255 == 1 BYTE == 8 Bit ) . You can use non-integer marker values, several binary channels with integer and non-integer values,  but event filters will be harder to perform, as comparisons are made at matlab calculation precision.  If you are using such a calibrated digital channel which is labelled 'marker' or 'signal', you can use the 'automatic' channel detection. In all other cases, you must choose the marker channel manually.
You can set a rounding precision for the marker channel in the marker options tab, on the \tools\options dialog. This can help filtering marker values that are not perfectly calibrated to integer values.

You can choose between 4 types of timing information: binary, digital, analog and fixed.

Select  'binary' to evaluate one or several data channels, that differentiate only between two values, such as 'on' and 'off', 0 and 1, or any two numbers.  Select 'digital' to evaluate one channel, that can code a distinct (and small) number of different values, such as numbers from 0 to 255 (= 1 BYTE / 8 BITS).  Select 'analog' to evaluate a continuously varying data channel (under construction). Select 'fixed' to generate timing data based only on filelength and filestarttime without a dedicated marker channel. Each timing type will be described separately in the following sections.

binary timing
If you have only one dedicated binary marker channel, anslab can load it automatically and extract timing information without further input.

In all other cases, for instance if you wish to use several binary marker channels as digits of a binary number, select manual channel selection, enter the number of channels to load, enter the sampling rate to operate with,  and choose the channels from a list of available channels.

Next, if you chose to load more than one channel, you can select how to integrate the signal from these channels:

Next you can enter a minimum event duration and  a maximum event duration. Event durations are measured from beginning of a new marker value to the next value change. Choosing '0' and 'inf' for minimum and maximum duration will cause anslab to write one timing line for every marker value change found in the ( integrated  ) marker signal.

The following dialog give you opportunity to specify special event numbers to extract and special event numbers to ignore. These options allow you to create timing files, that only contain events you are interested in for a specific analysis type. Choosing 'all' and 'none' for events to extract and events to ignore will cause anslab to write one timing line for every marker value change found in the ( integrated  ) marker signal.

After this, data is loaded, resampled and analyzed. You can choose to immediately view the created m-file in the matlab editor.

digital timing
The procedure for digital timing is identical to the one  described for binary timing, except that there are different integration operations available, if multiple marker channels are selected (+,-, logical and, logical or).

analog timing
(under construction)

fixed timing
Fixed timing refers to creating timing files based only one file start time and file length. 

Using this timing type, you can only create a number of intervals of constant length, either expressed as a fraction of the file length (relative) ...

or expressed in seconds (absolute)....