R-如何使用向量给定的参数运行函数列表中的每个函数

Question

Suppose I have a list of functions and a vector of parameter values:

functions <- list(a = function(x) x *2, b = function(x) x*3, c = function(x) x * 4)
paramVector <- c(2, 2, 1)

Now I want the following functionality of calling each function with the corresponding parameter and collating the result into a vector:

result <- c()
for (idx in 1:length(functions)) {
    result[idx] <- functions[[idx]](paramVector[idx])
}
result

Is there a way to do this without the for loop?

Answer 1

To iterate over the functions and paramVector objects at the same time, use Map. For example

Map(function(f,p) f(p), functions, paramVector)

Note that Map() always returns a list. You can also use mapply() which will attempt to simplify to a vector

mapply(function(f,p) f(p), functions, paramVector)