func_tau {binaryRL} | R Documentation |
Function: Soft-Max Function
Description
The softmax function describes a probabilistic choice rule. It implies
that options with higher subjective values are chosen with a greater
probability, rather than deterministic. This probability of choosing
the higher-valued option increases with the parameter tau
.
A higher tau
indicates greater sensitivity to value differences, making
choices more deterministic.
Usage
func_tau(
i,
L_freq,
R_freq,
L_pick,
R_pick,
L_value,
R_value,
var1 = NA,
var2 = NA,
LR,
try,
tau = 1,
alpha,
beta
)
Arguments
i |
The current row number. |
L_freq |
The frequency of left option appearance |
R_freq |
The frequency of right option appearance |
L_pick |
The number of times left option was picked |
R_pick |
The number of times left option was picked |
L_value |
The value of the left option with bias (if pi != 0) |
R_value |
The value of the right option with bias (if pi != 0) |
var1 |
[character] Column name of extra variable 1. If your model uses more than just reward and expected value, and you need other information, such as whether the choice frame is Gain or Loss, then you can input the 'Frame' column as var1 into the model.
|
var2 |
[character] Column name of extra variable 2. If one additional variable, var1, does not meet your needs, you can add another additional variable, var2, into your model.
|
LR |
Are you calculating the probability for the left option or the right option? |
try |
If the choice was random, the value is 1; If the choice was based on value, the value is 0. |
tau |
[vector] Parameters used in the Soft-Max Function. 'prob_func' representing the sensitivity of the subject to the value difference when making decisions. It determines the probability of selecting the left option versus the right option based on their values. A larger value of tau indicates greater sensitivity to the value difference between the options. In other words, even a small difference in value will make the subject more likely to choose the higher-value option.
|
alpha |
[vector] Extra parameters that may be used in functions. |
beta |
[vector] Extra parameters that may be used in functions. |
Value
The probability of choosing this option
Note
When customizing these functions, please ensure that you do not modify the arguments. Instead, only modify the 'if-else' statements or the internal logic to adapt the function to your needs.
Examples
## Not run:
func_tau <- function(
# Trial number
i,
# Number of times this option has appeared
L_freq,
R_freq,
# Number of times this option has been chosen
L_pick,
R_pick,
# Current value of this option
L_value,
R_value,
# Extra variables
var1 = NA,
var2 = NA,
# Whether calculating probability for left or right choice
LR,
# Is it a random choosing trial?
try,
# Free parameter
tau = 1,
# Extra parameters
alpha,
beta
){
if (!(LR %in% c("L", "R"))) {
stop("LR = 'L' or 'R'")
}
############################### [ value-based ] #############################
else if (try == 0 & LR == "L") {
prob <- 1 / (1 + exp(-(L_value - R_value) * tau))
}
else if (try == 0 & LR == "R") {
prob <- 1 / (1 + exp(-(R_value - L_value) * tau))
}
################################# [ random ] ################################
else if (try == 1) {
prob <- 0.5
}
else {
prob <- "ERROR" # Error check
}
return(prob)
}
## End(Not run)