Difference between revisions of "Export Single Trial Data"
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For the "''Interval...''" select a long enough time span as shown in figure 2: | For the "''Interval...''" select a long enough time span as shown in figure 2: | ||
| − | [[File:Export_epochs_2.png| | + | [[File:Export_epochs_2.png|none|213px|Figure 2 "Epoch around trigger" dialog]] |
Then click the "''Triggers...''" button to select which trigger code or condition will be used. | Then click the "''Triggers...''" button to select which trigger code or condition will be used. | ||
If you want to export the epochs around a trigger code: | If you want to export the epochs around a trigger code: | ||
Make sure that the trigger code you want is selected - e.g. the trigger code 1 in this example. | Make sure that the trigger code you want is selected - e.g. the trigger code 1 in this example. | ||
| − | |||
| − | + | [[File:Export_epochs_3.png|none|500px|Figure 3 "Trigger codes" dialog]] | |
[[File:Export_epochs_4.png|thumb|500px|Figure 4 "Epoch around condition" dialog]] | [[File:Export_epochs_4.png|thumb|500px|Figure 4 "Epoch around condition" dialog]] | ||
| + | |||
| + | If you want to export the epochs around a condition: Check the box "Conditions". Then ensure that the condition of choice is selected (e.g. condition "Rare" in the example. | ||
After clicking "OK" BESA Research either exports the data, or - if that option was chosen - sends the data to Matlab. | After clicking "OK" BESA Research either exports the data, or - if that option was chosen - sends the data to Matlab. | ||
| Line 54: | Line 55: | ||
The sub-structure data contains the latencies and the measured amplitudes for each channel and trial: | The sub-structure data contains the latencies and the measured amplitudes for each channel and trial: | ||
| + | |||
<tt> | <tt> | ||
| − | + | besa_channels.data | |
ans = | ans = | ||
Revision as of 16:27, 7 March 2016
Contents
Rationale
This article describes how to export single-trial EEG or MEG raw data for further analysis in an external program, e.g. in Matlab.
Steps to follow
1 Load data in BESA
The data are then displayed in the review window. Now you can either
- use the ERP module to define a condition and reject any trials with artifacts (see the BESA Help section on ERP for more information), or
- directly move to the export of all epochs around a particular trigger.
2 Export data from BESA
Select "File -> Export...". The export dialog opens:
Make sure that the options "Epochs around triggers" and "Original data" are selected. In the section "Target formats", choose the option of choice:
- If you want to create ASCII files for offline analysis, select "ASCII multiplexed" or "ASCII vectorized"
- If you want to analyze data directly in Matlab, select "Send to MATLAB"
For the "Interval..." select a long enough time span as shown in figure 2:
Then click the "Triggers..." button to select which trigger code or condition will be used. If you want to export the epochs around a trigger code: Make sure that the trigger code you want is selected - e.g. the trigger code 1 in this example.
If you want to export the epochs around a condition: Check the box "Conditions". Then ensure that the condition of choice is selected (e.g. condition "Rare" in the example.
After clicking "OK" BESA Research either exports the data, or - if that option was chosen - sends the data to Matlab. In case of Matlab, it opens the Matlab window and creates the structure "besa_channels". From Matlab save the structure as "besa_channels.mat".
3 Data in Matlab
The Matlab structure "besa_channels" contains several fields like in the following example of a 64-channel EEG file with 39 trials that survived the artifact scan:
datafile: [1x93 char]
channeltypes: {1x64 cell}
channellabels: {1x64 cell}
channelunits: {1x64 cell}
channelcoordinates: [64x9 double]
montage: 'Original'
filters: 'Filters off'
samplingrate: 100
HSPcoordinates: [3x3 double]
HSPtypes: {'Fiducial' 'Fiducial' 'Fiducial'}
HSPlabels: {'FidNz' 'FidT9' 'FidT10'}
headcenter: [-0.0020 8.1247e-004 0.0291]
headradius: 0.1021
electrodethickness: 0
structtype: 'besa_channels'
datatype: 'Epoched_Data'
data: [1x39 struct]
The sub-structure data contains the latencies and the measured amplitudes for each channel and trial:
besa_channels.data
ans =
1x39 struct array with fields:
amplitudes timeoffsetsecs latencies event
