Add columns definitions in the datasets doc (#672)

* Update datasets summary

* Rename #Trials column in MI table for consistency

* Update whatsnew

docs/source/dataset_summary.rst

@@ -17,10 +17,29 @@ there is a tutorial explaining how to do so, and we welcome warmly any new contr
 
 See also `Datasets-Support <https://github.com/NeuroTechX/moabb/wiki/Datasets-Support>`__ for supplementary
 detail on datasets (class name, size, licence, etc.)
+Dataset, #Subj, #Chan, #Classes, #Trials, Trial length, Freq, #Session, #Runs, Total_trials, PapersWithCode leaderboard
+
+Columns definitions:
+* **Dataset** is the name of the dataset.
+* **#Subj** is the number of subjects.
+* **#Chan** is the number of EEG channels.
+* **#Trials / class** is the number of repetitions performed by one subject for each class. This number is computed using only the first subject of each dataset. *The definitions of a **class** and of a **trial** depend on the paradigm used (see sections below)*.
+* **Trial length** is the duration of trial in seconds.
+* **Total_trials** is the total number of trials in the dataset (all subjects and classes together).
+* **Freq** is the sampling frequency of the raw data.
+* **#Session** is the number of sessions per subject. Different sessions are often recorded on different days.
+* **#Runs** is the number of runs per session. A run is a continuous recording of the EEG data. Often, the different runs of a given session are recorded without removing the EEG cap in between.
+* **PapersWithCode leaderboard** is the link to the dataset on the PapersWithCode leaderboard.
 
 Motor Imagery
 ======================
 
+Motor Imagery is a BCI paradigm where the subject imagines performing movements. Each movement is associated with a different command to build an application.
+
+Motor Imagery-specific definitions:
+* **#Classes** is the number of different imagery tasks.
+* **Trial** is one repetition of the imagery task.
+
 .. csv-table::
    :file: ../build/summary_imagery.csv
    :header-rows: 1
@@ -30,6 +49,12 @@ Motor Imagery
 P300/ERP
 ======================
 
+ERP (Event-Related Potential) is a BCI paradigm where the subject is presented with a stimulus and the EEG response is recorded. The P300 is a positive peak in the EEG signal that occurs around 300 ms after the stimulus.
+
+P300-specific definitions:
+* **A trial** is one flash.
+* **The classes** are binary: a trial is **target** if the key on which the subject focuses is flashed and **non-target** otherwise.
+
 .. csv-table::
    :file: ../build/summary_p300.csv
    :header-rows: 1
@@ -39,6 +64,13 @@ P300/ERP
 SSVEP
 ======================
 
+SSVEP (Steady-State Visually Evoked Potential) is a BCI paradigm where the subject is presented with flickering stimuli. The EEG signal is modulated at the same frequency as the stimulus. Each stimulus is flickering at a different frequency.
+
+SSVEP-specific definitions:
+* **#Classes** is the number of different stimulation frequencies.
+* **A trial** is one symbol selection. This includes multiple flashes.
+
+
 .. csv-table::
    :file: ../build/summary_ssvep.csv
    :header-rows: 1
@@ -58,6 +90,14 @@ Hornero, R. (2021). Brain–computer interfaces based on code-modulated visual e
 potentials (c-VEP): A literature review. Journal of Neural Engineering, 18(6), 061002.
 DOI: https://doi.org/10.1088/1741-2552/ac38cf
 
+c-VEP-specific definitions:
+* **A trial** is one symbol selection. This includes multiple flashes.
+* **#Trial classes** is the number of different symbols.
+* **#Epoch classes** is the number of possible intensities for the flashes  (for a visual cVEP paradigm). Typically, there are only two intensities: on and off.
+* **#Epochs / class** the number of flashes per intensity in each session.
+* **Codes** is the type of code used in the experiment.
+* **Presentation rate** is the rate at which the codes are presented.
+
 .. csv-table::
    :file: ../build/summary_cvep.csv
    :header-rows: 1

docs/source/whats_new.rst

@@ -19,6 +19,7 @@ Enhancements
 ~~~~~~~~~~~~
 
 - Update version of pyRiemann to 0.7 (:gh:`671` by `Gregoire Cattan`_)
+- Add columns definitions in the datasets doc (:gh:`672` by `Pierre Guetschel`_)
 
 Bugs
 ~~~~

moabb/datasets/summary_imagery.csv

@@ -1,4 +1,4 @@
-Dataset, #Subj, #Chan, #Classes, #Trials, Trial length, Freq, #Session, #Runs, Total_trials, PapersWithCode leaderboard
+Dataset, #Subj, #Chan, #Classes, #Trials / class, Trial length, Freq, #Session, #Runs, Total_trials, PapersWithCode leaderboard
 AlexMI,8,16,3,20,3s,512Hz,1,1,480,https://paperswithcode.com/dataset/alexandremotorimagery-moabb
 BNCI2014_001,9,22,4,144,4s,250Hz,2,6,62208,https://paperswithcode.com/dataset/bnci2014-001-moabb-1
 BNCI2014_002,14,15,2,80,5s,512Hz,1,8,17920,https://paperswithcode.com/dataset/bnci2014-002-moabb-1