Recipes for Non-Decision Time¶

General use of non-decision time¶

The simplest way to incorporate a non-decision time is to use the built-in `OverlayNonDecision`, for example:

```from pyddm import Model, Fittable, OverlayNonDecision
from pyddm.plot import model_gui
model = Model(overlay=OverlayNonDecision(nondectime=Fittable(minval=0, maxval=.8)),
dx=.01, dt=.01)
model_gui(model)
```

Gaussian-distributed non-decision time¶

```import numpy as np
import scipy
from pyddm import Overlay, Solution
class OverlayNonDecisionGaussian(Overlay):
name = "Add a Gaussian-distributed non-decision time"
required_parameters = ["nondectime", "ndsigma"]
def apply(self, solution):
# Make sure params are within range
assert self.ndsigma > 0, "Invalid st parameter"
# Extract components of the solution object for convenience
choice_upper = solution.choice_upper
choice_lower = solution.choice_lower
dt = solution.dt
# Create the weights for different timepoints
times = np.asarray(list(range(-len(choice_upper), len(choice_upper))))*dt
weights = scipy.stats.norm(scale=self.ndsigma, loc=self.nondectime).pdf(times)
if np.sum(weights) > 0:
weights /= np.sum(weights) # Ensure it integrates to 1
newchoice_upper = np.convolve(weights, choice_upper, mode="full")[len(choice_upper):(2*len(choice_upper))]
newchoice_lower = np.convolve(weights, choice_lower, mode="full")[len(choice_upper):(2*len(choice_upper))]
return Solution(newchoice_upper, newchoice_lower, solution.model,
solution.conditions, solution.undec)
```

Try it out with:

```from pyddm import Model, Fittable, OverlayNonDecision
from pyddm.plot import model_gui
model = Model(overlay=OverlayNonDecisionGaussian(
nondectime=Fittable(minval=0, maxval=.8),
ndsigma=Fittable(minval=0, maxval=.8)),
dx=.01, dt=.01)
model_gui(model)
```

Different non-decision time for left and right trials¶

Here we show an example of a non-decision time which depends on both the trial conditions and mulitiple parameters. In this case, we use a different non-decision time based on whether a stimulus was presented on the left or right side of the subject.

```import numpy as np
from pyddm import OverlayNonDecision, Solution
class OverlayNonDecisionLR(OverlayNonDecision):
name = "Separate non-decision time for left and right sides"
required_parameters = ["nondectimeL", "nondectimeR"]
required_conditions = ["side"] # Side coded as 0=L or 1=R
def get_nondecision_time(self, conditions):
assert conditions['side'] in [0, 1], "Invalid side"
return self.nondectimeL if conditions['side'] == 0 else self.nondectimeR
```

Try it out with:

```from pyddm import Model, Fittable, OverlayNonDecision
from pyddm.plot import model_gui
model = Model(overlay=OverlayNonDecisionLR(
nondectimeL=Fittable(minval=0, maxval=.8),
nondectimeR=Fittable(minval=0, maxval=.8)),
dx=.01, dt=.01)
model_gui(model, conditions={"side": [0, 1]})
```