Copying a vector into an array using Iterators - c++

Question

I've been attempting to copy a vector into an array with no luck. I'm not that familiar with iterators, which seem to be the best choice, but I've been unable to get the copy to work correctly. Here's the code:
// [[Rcpp::export]]
Rcpp::LogicalMatrix mateFamily(const Rcpp::LogicalVector& parent1,
const Rcpp::LogicalVector& parent2) {
// init
int i, AllCount, crossPt, crossCol;
AllCount = parent1.length();
Rcpp::LogicalVector child1(AllCount), child2(AllCount);
Rcpp::LogicalMatrix matePop(6,AllCount);
// print parents
std::cout << "parent1=" << parent1 << '\n';
std::cout << "parent2=" << parent2 << '\n';
// create 6 children
for (i = 0; i < 3; ++i) {
// determine crossover location
crossPt = i + 1;
crossCol = 3*(crossPt==1) + 6*(crossPt==2) + 9*(crossPt==3);
// swap
// child1 = parent1/parent2
std::copy(parent1.begin(), parent1.end(), child1.begin());
std::copy(parent2.begin()+crossCol, parent2.end(), child1.begin()+crossCol);
// child2 = parent2/parent1
std::copy(parent2.begin(), parent2.end(), child2.begin());
std::copy(parent1.begin()+crossCol, parent1.end(), child2.begin()+crossCol);
// print children
std::cout << "child1= " << child1 << '\n';
std::cout << "child2= " << child2 << '\n';
// copy children into matePop
std::copy(child1.begin(), child1.end(), matePop.begin()+i*AllCount);
std::copy(child2.begin(), child2.end(), matePop.begin()+i*AllCount);
}
std::cout << "matePop=" << '\n' << matePop << '\n';
return matePop;
}
The genetic crossover code works and creates the correct children combinations, but I can't figure out how to copy all 6 children into matePop.
The test parents as defined in R for this simplified example are:
parent1 <- cbind(1,1,1, 1,1,1, 1,1,1, 1,1,1)
parent2 <- cbind(0,0,1, 0,0,1, 0,0,1, 0,0,1)
Any help is greatly appreciated.
The crossover section works. Here's the output:
parent1= 1 1 1 1 1 1 1 1 1 1 1 1
parent2= 0 0 1 0 0 1 0 0 1 0 0 1
child1= 1 1 1 0 0 1 0 0 1 0 0 1
child2= 0 0 1 1 1 1 1 1 1 1 1 1
child1= 1 1 1 1 1 1 0 0 1 0 0 1
child2= 0 0 1 0 0 1 1 1 1 1 1 1
child1= 1 1 1 1 1 1 1 1 1 0 0 1
child2= 0 0 1 0 0 1 0 0 1 1 1 1
Here's the matePop output:
matePop=
100110011100
100110011100
111111111111
001110011001
001110011001
111111111111
So the mystery is when the children get copied into matePop

Answer 1

You should do this instead:
std::copy(child1.begin(), child1.end(), matePop.begin()+2*i*AllCount);
std::copy(child2.begin(), child2.end(), matePop.begin()+(2*i+1)*AllCount);
matePop is a 2d matrix with 6 rows and AllCount columns. So for the first time you'll be copying into rows 0 and 1. Second time into 2 & 3 and so on.