如何找到R中函数列表的总和？

Question

So i have a list of functions.I want to create a for loop that returns (obviously as a function) the sum of them.

In order to create a list of functions inside a for loop i am using this code

##CODE

f=dnorm
h=function(x){log(f(x))}

S=c(-3,-2,-1,0,1,2,3)
K=matrix(rep(1:length(S),2),ncol=2)

for(i in 1:length(S)){
   K[i,]=c(S[i],h(S[i]))
  }

funcs=list()

## LOOP TO DEFINE THE LINES

for(i in 1:6){

## Make function name
funcName <- paste( 'hl', i,i+1, sep = '' )

## Make function 
func1 = paste('function(x){  (K[',i,'+1,2]-K[',i,',2])/(K[',i,'+1,1]-K[',i,',1])*x+ 
K[',i,'+1,2]-((K[',i,'+1,2]-K[',i,',2])/(K[',i,'+1,1]-K[',i,',1]))*K[',i,'+1,1]}',sep 
= '')

funcs[[funcName]] = eval(parse(text=func1))

 }

which creates a list of 6 functions. How can I get their sum? I tried using the apply commands but either my syntax is not correct or they do not work.

PS I am actually trying to write my one code for the ars command.

Answer 1

As Nick pointed out, "the sum of functions" doesn't make sense. I'm wildly guessing that you want to evaluate at function at some point (at S ?) and then take the sum of those values. This should do the trick.

rowSums(sapply(funcs, function(f) f(S)))

---

Much of your code can be written more cleanly, and in a vectorised way.

f <- dnorm
h <- function(x) log(f(x))

S <- -3:3
K <- cbind(S, h(S))  #No need to define this twice; no need to use a loop 

i <- seq_len(6)
funcNames <- paste('hl', i, i+1, sep = '') #paste is vectorised

#You can avoid using `paste`/`eval`/`parse` with this function to create the functions
#Can possibly be done even more cleanly by using local
makeFunc <- function(i)
{
  evalq(substitute(
    function(x)
    {  
      (K[i + 1, 2] - K[i, 2]) / (K[i + 1, 1] - K[i, 1]) * x + 
      K[i + 1, 2] - 
      ((K[i + 1, 2] - K[i, 2]) / (K[i + 1, 1] - K[i, 1])) * K[i + 1, 1]
    }, 
    list(i = i)
  ))
}

funcs <- lapply(i, makeFunc)
names(funcs) <- funcNames
rowSums(sapply(funcs, function(f) f(S)))