How to create case variables

Case variables represent a selected trial or the sum, average, etc. of a range of trials of a given case. In the resulting scrollsheet, case variables are represented as columns with one cell per case. For most variable types, the Analyze Case Document command leaves you a choice of either analyzing all trials in a case or to restrict the analysis to a particular range of trials. However, because case variables that were computed following the instructions of a custom variable definition file already refer to an explicitly defined range or combination of trials, their definition can no longer be modified by the Analyze Case Document command.

Two sequences of statements that you can use to define a case variable are detailed below. Which one you choose depends on the type of information you want to be captured by the variable. If you you are mainly interested in temporal changes of a measure, the definition of a case variable will involve a data matrix and a data array as intermediary result. If, however, you want to focus on the spatial distribution of a measure, calculation of the case variable will also involve the creation of a data surface.

Capturing temporal changes using case variables...

1. Create an active data matrix and selection mask using an appropriate combination of Matrix, Memory, Transform, Include and Exclude statements.
2. If you wish to limit the analysis to just a portion or time window of the trials, use the Window statement to set that window. If you omit the Window statement, all data points will be considered.
3. Use the Collapse statement to collapse the data matrix into a data array. Each element of a data array stands for one column of the data matrix, that is for one trial. Wintrack provides storage for 50 data arrays, referred to as a01-a10. The Collapse statement does not actually destroy the active data matrix. You can use it repeatedly to create several data arrays from the same data matrix, e.g. containing maxima, minima, and averages of columns.
4. The active data matrix from which a data array is derived may refer to a field which is not applicable to all trials. You might want to apply the Verify statement to a data array, to assure that all elements corresponding to trials, to which a given field is not applicable, will be replaced by missing value codes.
5. Use the Extract statement to extract a single data value from a data array you have created, e.g. by calculating the sum or the average of its elements. Wintrack provides storage for 100 data values, referred to as v001-v100. You can also use an expression referring to more than one data array as a source for a data value. In that case the data arrays are combined element by element. You can apply the Extract statement several times to extract different data values from the same data array.
6. Use the Tabulate statement to create a case variable based on one of the data values you have created. A case variable reports the content of a data value as a single cell in the resulting scrollsheet. You can also use an expression referring to more than one data value as a source for a case variable. You can use the Tabulate statement repeatedly to create more than one case variable based on the same set of data values. As the variable definition file is later applied to a range of trials using the Analyze Case Document command, each Tabulate statement will add a new column to the resulting scrollsheet. At the beginning of the analysis, Wintrack will automatically create two columns listing the case name and case number for each row.
7. You may repeat steps 1 through 7 as many times as you wish, in order to create a set of case variables that report data from different data matrices.

Capturing spatial distribution using case variables...

1. Create an active data matrix and selection mask using an appropriate combination of Matrix, Memory, Transform, Include and Exclude statements.
2. If you wish to limit the analysis to just a portion or time window of the trials, use the Window statement to set that window. If you omit the Window statement, all data points will be considered.
3. Use the Surface statement to represent the spatial distribution of data matrix values as a data surface. Its cells represent rectangular tiles which fill the surface of the arena. Data surfaces representing case documents with more than one trial have multiple trial planes, one for each trial in the case. Wintrack provides storage for 5 data surfaces, referred to as s1-s5. The Surface statement does not actually destroy the active data matrix. You can use it repeatedly to create several data surfaces from the same data matrix.
4. Apply the Collect statement to compute a data array representing a relevant aspect of the data surface with one value for each trial plane. Wintrack provides storage for 50 data arrays, referred to as a01-a10. You can apply the statement several times to compute different data values from the same data surface.
5. Use the Extract statement to extract a single data value from a data array you have created, e.g. by calculating the sum or the average of its elements. Wintrack provides storage for 100 data values, referred to as v001-v100. You can also use an expression referring to more than one data array as a source for a data value. In that case the data arrays are combined element by element. You can apply the Extract statement several times to extract different data values from the same data array.
6. Use the Tabulate statement to create a case variable based on one of the data values you have created. A case variable reports the content of a data value as a single cell in the resulting scrollsheet. You can also use an expression referring to more than one data value as a source for a case variable. You can use the Tabulate statement repeatedly to create more than one case variable based on the same set of data values. As the variable definition file is later applied to a range of trials using the Analyze Case Document command, each Tabulate statement will add a new column to the resulting scrollsheet. At the beginning of the analysis, Wintrack will automatically create two columns listing the case name and case number for each row.
7. You may repeat steps 1 through 6 as many times as you wish, in order to create a set of case variables that report data from different data matrices.

Additional information...

• How to use conditional trial discarding explains how to discard trials based on analysis results.
• Managing custom variable definition files provides general information on the management of custom variable definition files.
• The Flowchart of advanced data analysis gives a synopsis of data and variable types.
• How to define variable blocks explains how to define case variables more efficiently by grouping them into variable blocks.
• Using the Memory statement you can build collections of data matrices and selection masks for later reuse in other variables.
• There is a topic describing how to build a custom variable definition file.
• There is a list of all available variable definition statements.
• See Analyze Case Document command for basic information on that command.
• Inside case documents provides advanced information on case documents.