add support for binary parameters (#454)

Summary:

Binary parameters are just secretly discrete parameters bounded at [0, 1].  Config will accept binary as a par_type and do the necessary work to support it in modeling.

Differential Revision: D65954134

aepsych/config.py

@@ -182,8 +182,8 @@ def update(
                     # Validate the parameter-specific block
                     self._check_param_settings(par_name)
 
-                    lb[i] = self[par_name]["lower_bound"]
-                    ub[i] = self[par_name]["upper_bound"]
+                    lb[i] = self[par_name].get("lower_bound", fallback="0")
+                    ub[i] = self[par_name].get("upper_bound", fallback="1")
 
                 self["common"]["lb"] = f"[{', '.join(lb)}]"
                 self["common"]["ub"] = f"[{', '.join(ub)}]"
@@ -276,6 +276,11 @@ def _check_param_settings(self, param_name: str) -> None:
                 and self.getint(param_name, "upper_bound") % 1 == 0
             ):
                 raise ValueError(f"Parameter {param_name} has non-integer bounds.")
+        elif param_block["par_type"] == "binary":
+            if "lower_bound" in param_block or "upper_bound" in param_block:
+                raise ValueError(
+                    f"Parameter {param_name} is binary and shouldn't have bounds."
+                )
         else:
             raise ValueError(
                 f"Parameter {param_name} has an unsupported parameter type {param_block['par_type']}."

aepsych/transforms/parameters.py

@@ -171,8 +171,8 @@ def get_config_options(
             except KeyError:  # Probably because par doesn't have its own section
                 par_type = "continuous"
 
-            # Integer variable
-            if par_type == "integer":
+            # Integer or binary variable
+            if par_type in ["integer", "binary"]:
                 round = Round.from_config(
                     config=config, name=par, options=transform_options
                 )
@@ -196,7 +196,9 @@ def get_config_options(
                 transform_dict[f"{par}_Log10Plus"] = log10
 
             # Normalize scale (defaults true)
-            if config.getboolean(par, "normalize_scale", fallback=True):
+            if config.getboolean(
+                par, "normalize_scale", fallback=True
+            ) and par_type not in ["discrete", "binary"]:
                 normalize = NormalizeScale.from_config(
                     config=config, name=par, options=transform_options
                 )

docs/parameters.md

@@ -15,6 +15,7 @@ what parameter types are used and whatever transformations are used.
 Currently, we only support continuous parameters. More parameter types soon to come!
 
 <h3>Continuous<h3>
+
 ```ini
 [parameter]
 par_type = continuous
@@ -28,6 +29,7 @@ include negative values (e.g., lower bound = -1, upper bound = 1) or have very l
 ranges (e.g., lower bound = 0, upper bound = 1,000,000).
 
 <h3>Integer<h3>
+
 ```ini
 [parameter]
 par_type = integer
@@ -40,6 +42,25 @@ and necessity of bounds. However, integer parameters will use continuous relaxat
 allow the models and generators to handle integer input/outputs. For example, this could
 represent the number of lights are on for a detection threshold experiment. 
 
+<h3>Binary</h3>
+
+```ini
+[parameter]
+par_type = binary
+```
+
+Binary parameters could be useful for modeling parameters like whether a distractor is 
+on or not during a detection task. Binary parameters are implemented as a special case 
+of a integer parameter. No bounds should be set. It will be treated as a integer 
+parameter that will either be 0 or 1. Binary parameters are equivalent to this: 
+
+```ini
+[parameter]
+par_type = discrete
+lower_bound = 0
+upper_bound = 1
+```
+
 <h2>Parameter Transformations</h2>
 Currently, we only support a log scale transformation to parameters. More parameter
 transformations to come! In general, you can define your parameters in the raw

tests/test_transforms.py

@@ -17,7 +17,7 @@
     ParameterTransformedModel,
     ParameterTransforms,
 )
-from aepsych.transforms.ops import Log10Plus, NormalizeScale
+from aepsych.transforms.ops import Log10Plus, NormalizeScale, Round
 
 
 class TransformsConfigTest(unittest.TestCase):
@@ -448,3 +448,55 @@ def test_integer_model(self):
         est_max = x[np.argmin((zhat - target) ** 2)]
         diff = np.abs(est_max / 100 - target)
         self.assertTrue(diff < 0.15, f"Diff = {diff}")
+
+    def test_binary(self):
+        config_str = """
+            [common]
+            parnames = [signal1]
+            stimuli_per_trial = 1
+            outcome_types = [binary]
+            strategy_names = [init_strat]
+
+            [signal1]
+            par_type = binary
+
+            [init_strat]
+            generator = SobolGenerator
+            min_asks = 1
+        """
+        config = Config()
+        config.update(config_str=config_str)
+
+        strat = SequentialStrategy.from_config(config)
+
+        transforms = strat.transforms
+
+        self.assertTrue(len(transforms) == 1)
+        self.assertTrue(isinstance(list(transforms.values())[0], Round))
+        self.assertTrue(
+            torch.all(config.gettensor("common", "lb") == torch.tensor([0]))
+        )
+        self.assertTrue(
+            torch.all(config.gettensor("common", "ub") == torch.tensor([1]))
+        )
+
+        bad_config_str = """
+            [common]
+            parnames = [signal1]
+            stimuli_per_trial = 1
+            outcome_types = [binary]
+            strategy_names = [init_strat]
+
+            [signal1]
+            par_type = binary
+            lower_bound = 0
+            upper_bound = 1
+
+            [init_strat]
+            generator = SobolGenerator
+            min_asks = 1
+        """
+        config = Config()
+
+        with self.assertRaises(ValueError):
+            config.update(config_str=bad_config_str)