Exported or converted CSV files contain the same descriptive tags and columns of data as the EDF files for EEG and motion data, but in CSV format. When exporting a recording as a CSV file, you will get 2 files - one for EEG and one for motion data (named “...md.csv”) if motion data was collected from your headset.
Please note: Epoc Flex currently support EEG and Frequency Band data only. Motion or Performance Metrics data is not supported
You can also export CSV files for Performance Metrics and Frequency Band data. See the formats for these exported files below:
Performance metrics data
Performance metrics data is exported in CSV format only and at a frequency of 0.1Hz.
The first row of the Performance Metric files (named "...pm.csv") contains the headings for each column of data. In order, they are as follows:
Timestamp contains the timestamp of the sample in seconds.
The timestamp value is explicitly related to the number of seconds after the headset connected to the application that the sample was taken.
To get the actual time of a sample, you can add the timestamp value of a sample to thetimestamp startedvalue of the session found in the EEG file:
REAL TIME =timestamp started (ms)+ timestamp*1000
The data columns for the Performance metric data. Each of the six metrics has five data columns associated with it, each tagged with the following suffixes:
_ENG - Engagement
_VAL - Interest
_MED - Relaxation
_FRU - Stress
_FOC - Focus
_EXC - Excitement (short-term)
For each metric, there are five data columns, labeled with the following prefixes:
SCA - The Scaled Data column shows the Raw Data scaled to fit on a 0 to 1 scale to provide more context for each individual's scores. The scaling is based on a successive approximation of the mean and variance for each recording, calculated as the session progresses. The data file reflects this progressive scaling which usually stabilizes after a few minutes.
RAW - The Raw Data column shows the raw values outputted from our Performance Metrics algorithm which can range from single digit negative numbers to single digit positive numbers. Different individuals can have non-overlapping ranges. These numbers are meaningful when looked at relatively.
MIN/MAX- MIN and MAX values set lower and upper bounds for the Scaled Data and are calculated from the current mean and variance of the Raw Data. Initial values of MIN and MAX are set based on population data. The current value is scaled so that MIN maps to .05 and MAX maps to .95 on the 0-1 scale. We use a logistic scale to prevent data cutoff at 0 and 1 boundaries; the range around the mean value (mapped to 0.5) is close to linear while the extremes get steadily more nonlinear.
ACT - The Active Flag is 1 when the Performance Metric is active and 0 when the Performance Metric is not active due to poor signal quality and/or noise.
To scale the Raw Data post hoc for a given recording, you can use the MIN and MAX values at the end of the recording (where they are most stable) and the following equation: