Why is this r code not creating a vector? - r

Question

I am trying to create a vector that will save the vector vprime for graphing later, but it wont't show up in my local environment (it is not writing the vector). Any ideas??
Thanks!!
###plot all three at once###
space<-seq(length=100, from=0, to=7.2) ##Create a sequence of 100 values ending at the point where value goes negative
A<- 4 #take a as given
alpha<-0.3 #take alpha as given
beta<-0.98 #take beta as given
vprime3 <- c(1:100) ##create a vector length 100 to be replaced later
t_vj3 <- c(1:100) ##create a vector length 100 to be replaced later
iterater<-function(space){ ##create a function to perform the iteration
for(i in 1:100){ ##create for loop for one of the state space (varying k+1)
for(j in 1:100){ ##create for loop for another axis of the state spcae (varying k)
if((A*(space[i]^alpha)-space[j])<0){ #plug in the law of motion
t_vj3[j]=-99 #and have a case for negative consumption so it does not take a negative log
}
else {
t_vj3[j+1] <- (log(A*(space[i]^alpha)-space[j])+ beta*t_vj3[j]) #have the law of motion for positive values
}
}
vprime3[i]<-max(t_vj3) #and create a vector of the maximum values, or the value functions
}
a4<-vprime3
plot(space,vprime3, type="p", xlab="State Space", ylab="Value") # and plot this graph
}
iterater(space) #call the function

Answer 1

It is creating the vector in the environment of the function body. That environment, and thus the vector goes away once the function returns.
There are two ways to get the value: Return the value and capture it, or modify the enclosing environment directly.
To return the value, change the function as follows:
iterater<-function(space){
# ....
a4<-vprime3
plot(space,vprime3, type="p", xlab="State Space", ylab="Value") # and plot this graph
# Added line
return(a4)
}
## Call iterater, saving the value:
a4 <- iterater(space)
Modifying the enclosing environment seems easy, but leads to trouble down the road, so this approach should be avoided. But to do this, change the function as follows:
iterater<-function(space){
# ....
# Note <<- instead of <-
a4<<-vprime3
plot(space,vprime3, type="p", xlab="State Space", ylab="Value") # and plot this graph
}