How to fix Object(...) not found while it is declared in R - r

Question

I am trying to take a derivative of a double sum function. I am running into this error:
Error in deriv.f.1(X = X.data, y = y.vec, alpha = alpha.vector[1, ]) :
object 'L_D_grad' not found
I have tried to move the {} brackets around, double check if I missed a closing/opening bracket, if I have extra opening/closing bracket. However, the error still exists.
# Generate Sample Data
gen.sample <- function(n){
x <- rnorm(n,5,10)
y <- ifelse(x < 2.843,1,-1)
return(data.frame(x,y))
}
##
deriv.f.1 <- function(X,y,alpha){
N <- length(X)
L_D_grad < numeric(N)
xy.alpha.sum <- numeric(N)
for(k in 1:N){
for(l in 1:N){
if(l == k){
xy.alpha.sum[l] = 0}
else{
xy.alpha.sum[l] <- alpha[l]*y[k]*y[l]*X[k]*X[l]}
}
L_D_grad[k] <- 1 - sum(xy.alpha.sum) - alpha[k]*(y[k])^2*(X[k])^2
}
return(L_D_grad)
}
## Illustration
set.seed(4997)
options(digits = 4,scipen = -4)
sample.data <- gen.sample(n=N)
X.data <- sample.data$x
y.vec <- sample.data$y
alpha.vector <- matrix(rep(seq(from=-5,to = 5, length.out = N),N*N),
ncol = N, nrow = N, byrow = TRUE)
alpha_vec <- alpha.vector[1,]
deriv.f.1(X = X.data, y = y.vec, alpha = alpha_vec)
Thanks in advance!

Answer 1

Here is my code:
# Generate Sample Data
gen.sample <- function(n){
x <- rnorm(n,5,10)
y <- ifelse(x < 2.843,1,-1)
return(data.frame(x,y))
}
##
deriv.f.1 <- function(X,y,alpha){
N <- length(X)
L_D_grad <- numeric(N)
xy.alpha.sum <- numeric(N)
for(k in 1:N){
for(l in 1:N){
if(l == k){
xy.alpha.sum[l] = 0}
else{
xy.alpha.sum[l] <- alpha[l]*y[k]*y[l]*X[k]*X[l]}
}
L_D_grad[k] <- 1 - sum(xy.alpha.sum) - alpha[k]*(y[k])^2*(X[k])^2
}
return(L_D_grad)
}
## Illustration
set.seed(4997)
options(digits = 4,scipen = -4)
N=10
sample.data <- gen.sample(n=N)
X.data <- sample.data$x
y.vec <- sample.data$y
alpha.vector <- matrix(rep(seq(from=-5,to = 5, length.out = N),N*N),
ncol = N, nrow = N, byrow = TRUE)
alpha_vec <- alpha.vector[1,]
deriv.f.1(X = X.data, y = y.vec, alpha = alpha_vec)
Where:
#sample.data
#x y
#1 -5.303e+00 1
#2 1.493e+01 -1
#3 9.797e+00 -1
#4 1.991e+01 -1
#5 -1.454e+01 1
#6 1.423e+01 -1
#7 1.025e+01 -1
#8 5.455e+00 -1
#9 3.719e+00 -1
#10 2.021e+01 -1
And deriv.f.1(X = X.data, y = y.vec, alpha = alpha_vec)
# -1.271e+01 -3.759e+01 -2.432e+01 -5.046e+01 -3.659e+01 -3.577e+01 -2.548e+01 -1.310e+01
# -8.612e+00 -5.123e+01
I made two changes:
Assign N a value: N=10
Correct assignment form L_D_grad: L_D_grad <- numeric(N)