How to loop a function in r?

Question

Example: 
a <- function(b,c,d,e,f){ 
if(f == 1){
  Value1 <- b * c * d * e
  return(Value1)
}else if(f == 2){
  Value2 <- b * c * d
  return(Value2) 
}else{
  Value3 <- 0 
}
}

Assume I would like to analyze the relationship between Value2 and d for d = seq(0,2,0.05) if b,c,e are fixed and I can't change the function. So I would like to plot a graph with Value2 on the y-axis and d on the x-axis. What I tried: Construct a vector and combine them with seq(0,2,0.05)

ValueChange <- c() 

for( i in seq(0,2,0.05)){
  ValueChange <- a(10,2,i,5,2)
}
ValueChange

Unfortunately, that didn't work

ThomasIsCoding · Accepted Answer · 2020-04-28 20:11:29Z

1

Maybe your for loop should be like below

for( i in seq(0,2,0.05)){
  ValueChange <- c(ValueChange,a(10,2,i,5,2))
}

where the newly generated value a(10,2,i,5,2) will be updated and appended to ValueChange

Or a more efficient way via sapply

ValueChange <- sapply(seq(0,2,0.05),function(i) a(10,2,i,5,2))

edited Apr 28, 2020 at 20:11

answered Apr 28, 2020 at 20:07

ThomasIsCoding

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2 Comments

John Coleman Over a year ago

Isn't that an O(n^2) way of creating the vector?

ThomasIsCoding Over a year ago

@JohnColeman I know it is inefficient. An efficient way might be sapply. I just want to show OP what happened in the for loop

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