Hello,
The functions are not equivalent.
integrate subdivides the interval lower = 0, upper = 10 in into a
maximum subdivisions = 100L. If you print length(X) you will see that
it's 21.
X is a vector of 21 values and to compute X^(1:10) this expands to
X[1]^1, X[2]^2, ..., X[10]^10, X[11]^1, X[12]^2, ..., X[20]^10, X[21]^1
Each of these values is multiplied by a*b and then added.
A total different computation is performed by the second function:
X[1:21]^1, X[1:21]^2, etc.
I have rewrote the functions a bit, without the print statements and in
myfun2 creating the list term beforehand.
myfun <- function(X, a, b){
k <- 1:10
term <- a * b * X^k
fx <- exp(X) * sum(term)
fx
}
myfun2 <- function(X, a, b){
term <- vector("list", length = 10)
for(k in 1:10){
term[[k]] <- a * b * X^k
}
fx <- exp(X) * sum(unlist(term))
fx
}
a <- 5
b <- 4
integrate(myfun, lower = 0, upper = 10, a = a, b = b)
integrate(myfun2, lower = 0, upper = 10, a = a, b = b)
curve(myfun(x, a = a, b = b), 0, 10)
curve(myfun2(x, a = a, b = b), 0, 10, col = "blue", add = TRUE)
Hope this helps,
Rui Barradas
Às 04:14 de 18/07/2020, Shaami escreveu:
Hi Everyone
It has been a long time I am facing a problem with integrating a function
that contains for-loop or even vectorization of for loop. Could you please
guide for the following MWE that how I could get rid of the error or
warning messages?
My MWE code is here:
myfun <- function(X, a, b){
k <- 1:10
term <- a * b * X^k
fx <- exp(X) * sum(term)
print(X)
print(term)
return(fx)
}
a <- 5
b <- 4
integrate(myfun, lower = 0, upper = 10, a = a, b = b)
If I use the following version of my code, it does not give any error.
However, I am not sure that it is correct.
myfun <- function(X, a, b){
term <- list()
for(k in 1:10){
term[[k]] <- a * b * X^k
}
fx <- exp(X) * sum(unlist(term))
print(X)
print(term)
return(fx)
}
a <- 5
b <- 4
integrate(myfun, lower = 0, upper = 10, a = a, b = b)
Thank you
Regrads
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