This is an overview of all functions available within the DQL. Functions can be used to aggregate (sum, average ..) or do custom tranformations (ceiling, flooring, …)
The avg function is an aggregation function and calculates the average of all values passed as a parameter and returns the result.
The chisquare function calculates the chisquare significance based on the submitted values. If the chisquare test is not appropriate, it will return null.
The coalesce function is used to transform a null value into something useful. If the parameter passed to coalesce is null, the second parameter will be returned and otherwise the first parameter.
The count function is an aggregation function and returns the amount of rows fetched from the dataset.
The cumulate function does the same as the sum function, but is no aggregation function.
This allows cumulative representations of data.
The distinctcount function is very similar to the count function, but only counts distinct values - duplicates are ignored.
The if function is used to apply a condition on a column. The first parameter is a condition, the second parameter is returned if the condition returns true and the third parameter is returned if the condition is false.
The max function is an aggregation function which is capable of returning the maximum value from a column in a group.
The min function is an aggregation function which allows to extract the lowest value from a group. The opposite function of this is the max function.
The participates function returns a flag, saying whether an experiment participates in an entity or not.
For instance, this is useful to determine whether a session participates in an experiment.
The pres function can be used to read the result of the psum function for a single channel which comes from the experiment.
The psum function is an aggregation function and can be used on participation fields. It will sum the participations together and return a total sum mask for all channels.
The round function rounds the values down to zero decimal places, or to the amount of decimal places submitted in the second parameter.
The standard deviation function is an aggregation function which calculates the standard deviation of the submitted values.
The sum function is an aggregation function, it rolls all rows together and returns the total sum of the values submitted in the parameter.
The time function returns the current time, in the same way as they are stored in all time columns. It returns the amount of seconds passed since 1970.
The timefloor function rounds the time value to the closest interval value. This allows grouping based on time.
The variation function is an aggregation function and calculates the variation of the submitted values.