sample_density
sample_density.RdSample a smooth fixation density map with a set of discrete fixations.
This function samples a smooth fixation density map represented by the object x with a set of discrete fixations provided in fix.
Usage
sample_density(x, fix, ...)
# S3 method for class 'density'
sample_density(
x,
fix,
times = NULL,
normalize = c("none", "max", "sum", "zscore"),
...
)Arguments
- x
An object of class "density" representing the smooth fixation density map.
- fix
A data frame or tibble containing discrete fixations with columns "x", "y", and "onset".
- ...
Additional arguments passed on to the method, including
normalize(one of"none","max","sum", or"zscore") to control density map normalization before sampling.- times
A vector of numeric values representing the time points at which the density map should be sampled (default is NULL).
- normalize
A character string specifying how to normalize the density map before sampling. One of:
"none"No normalization (default). Returns raw density values.
"max"Divide by the maximum density value, yielding values in [0, 1].
"sum"Divide by the sum of all density values, yielding a probability distribution.
"zscore"Z-score the density map (subtract mean, divide by SD). Useful for comparing across maps with different scales.
Value
A data frame with columns 'z' (density estimates at fixation locations) and 'time' (onset time of fixations).
A data frame with columns "z" and "time", where "z" contains the sampled density values and "time" contains the corresponding time points.
Details
This function samples a given smooth fixation density map with a set of discrete fixations to estimate the density at the locations of those fixations.
The function first checks if the times parameter is NULL. If so, it directly samples the density map using the coordinates of the fixations in the fix argument. If the times parameter is provided, the function first calls the sample_fixations function to generate a new fixation sequence with the specified time points, and then samples the density map using the coordinates of the new fixation sequence. The result is a data frame containing the sampled density values and the corresponding time points.