Fast-dm is free open-source software for the estimation of diffusion model parameters. It is a command-line tool that reads commands from a text file (by default named experiment.ctl). Below, we present an overview of possible commands for the control file. A more thorough description is provided by Voss & Voss (2007).
To run fast-dm you have to save the control file, all your data files and fast-dm.exe in the same directory. Then you can start fast-dm by a double click. However, we recommend starting it from a command window so that you have a chance to inspect possible error messages. You can give the name of the control file as an option (e.g., enter fast-dm exp1.ctl); if no option is entered, fast-dm tries to load the file experiment.ctl.
Commands for the Control File
| Command | Explanation | Examples |
|---|---|---|
| method CRITERION | Selection of estimation procedure (Maximum Likelihood; Kolmogorov-Smirnov; Chi-Square). | - method ml - method ks - method cs |
| precision VALUE | Precision of calculation. VALUE corresponds roughly to the number of decimals of the predicted CDFs that are calculated accuratly. | - precision 2.5 - precision 5.0 |
| set PARAMETER VALUE | Fix a parameter to a specific value; this parameter will not be estimated by fast-dm. | - set zr 0.5 - set d 0 |
| depends PARAMETER CONDITION | Denotes that this parameter may vary between different trial types or conditions. CONDITION need to be defined later by the format command | - depends v stimulus - depends a block |
| format CONDITION ... | Defines the variable names for the columns of the data file(s). The format command is always required, and you need to define always the variables RESPONSE and TIME (using capital letters). In the data files, responses have to be coded as 0 (lower threshold) or 1 (upper threshold). Times have to be given in seconds (not: ms!). | - format block stimulus RESPONSE TIME - format * * RESPONSE TIME |
| load FILENAME | Defines the names of input files (required command). | - load data.dat - load*.dat |
| save FILENAME | Defines the names of separate output files (one output file for each data set). Either the save or the log command are required. | - save parameter.dat - save*.par |
| log FILENAME | Defines the names of a common output file (one output file for all data sets). Either the save or the log command are required. | - log parameter.lst |
Example of a complete control file
method ks
precision 3
set zr 0.5
set d 0
set szr 0
set sv 0
set p 0
depends v stimulus
format stimulus RESPONSE TIME
load*.dat
log parameter.lst