Passing more than 2 vectors in R [duplicate] - r

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Trying to pass more than 2 vectors to a function in R
(2 answers)
Closed 5 years ago.
I want to compute e^(ax+b) over a=-1:1 and b=-1:1 for various values of X. I want the output in the form a list of 5 elements. Each element in the list is 3X3 Matrix.
I did achieve this using Outer and Vectorize.
sigm = function(a=0,b=0,x){
return(exp(x*a+b))
}
sigm1 = Vectorize(function(a=-1:1,b=-1:1,x){
outer(a,b,sigm,x)
},SIMPLIFY = FALSE)
Now, sigm1(x=1:3) gives the required output
[[1]]
[,1] [,2] [,3]
[1,] 0.1353353 0.3678794 1.000000
[2,] 0.3678794 1.0000000 2.718282
[3,] 1.0000000 2.7182818 7.389056
[[2]]
[,1] [,2] [,3]
[1,] 0.04978707 0.1353353 0.3678794
[2,] 0.36787944 1.0000000 2.7182818
[3,] 2.71828183 7.3890561 20.0855369
[[3]]
[,1] [,2] [,3]
[1,] 0.01831564 0.04978707 0.1353353
[2,] 0.36787944 1.00000000 2.7182818
[3,] 7.38905610 20.08553692 54.5981500
The only draw back with this code snippet is I am using the default values of a=-1:1 and b=-1:1. When I try to pass the same during function calling, it goes haywire. E.g.
sigm1(-1:1,-1:1,1:3)
[[1]]
[,1]
[1,] 0.1353353
[[2]]
[,1]
[1,] 1
[[3]]
[,1]
[1,] 54.59815
I am unable to figure out why passing the arguments is making this difference in output.

Answer 1

You could use sapply to create your vectorized function
sigm = function(a, b, x){
return(lapply(x, function(xx) sapply(b, function(bb)
sapply(a, function(aa) exp(xx*aa+bb)))))
}
sigm(a = -1:1, b = -1:1, x = 1:3)
#[[1]]
# [,1] [,2] [,3]
#[1,] 0.1353353 0.3678794 1.000000
#[2,] 0.3678794 1.0000000 2.718282
#[3,] 1.0000000 2.7182818 7.389056
#[[2]]
# [,1] [,2] [,3]
#[1,] 0.04978707 0.1353353 0.3678794
#[2,] 0.36787944 1.0000000 2.7182818
#[3,] 2.71828183 7.3890561 20.0855369
#[[3]]
# [,1] [,2] [,3]
#[1,] 0.01831564 0.04978707 0.1353353
#[2,] 0.36787944 1.00000000 2.7182818
#[3,] 7.38905610 20.08553692 54.5981500