3D Vector - "No instance of overload function?" - c++

Question

Still relatively new to vectors in C++, the aim of this function is to take 4 arguments, 3 of which define the (x , y , z) position of the data being written, and the 4th being the value that is to be written.
as Requested, a picture of the errors is listed:
Picture of code listed above
The issue is under the "push_back" code. the "." after yy.push and xx.push is giving the error "no instance of overloaded function".
If somebody could explain what this means and how to fix it I would greatly appreciate it! :)
double datawrite(vector<unsigned int> xx, vector<unsigned int> yy,
vector<unsigned int> zz, double val) {
//Writes data to the 3d Vector
//finds coordinates for data
vector< vector< vector<unsigned int > > > xx;
vector< vector<unsigned int> > yy;
vector<unsigned int> zz;
//Writes value at proper position
zz.push_back(val);
yy.push_back(zz);
xx.push_back(yy);
//outputs value from vector
return val;
}

Answer 1

So you want a 3d matrix of doubles? First you need to create it:
#include <vector>
std::vector<vector<vector<double>>> matrix;
This creates a 3d matrix, but with 0 size. Next, when you add data to the matrix, you need to make sure the matrix is big enough:
// Co-ords are integers
double datawrite(int x, int y, int z, double val)
{
// Make sure vectors are large enough
if (matrix.size() < x+1) matrix.resize(x+1);
if (matrix[x].size() < y+1) matrix[x].resize(y+1);
if (matrix[x][y].size() < z+1) matrix[x][y].resize(z+1);
// Store the value
matrix[x][y][z] = val;
return val;
}
However, this is a bit messy and leaves the matrix in an incomplete state. For example, if you call datawrite(2, 3, 4, 9.9); this may appear that all indexes < 2,3,4 would be valid, but they are not. For example trying to read matrix[0][0][0] will give you an error.
You could work around this with a dataread function that checks the sizes of the vectors before trying to read from them.
If you know ahead of time how large the matrix is, you can create the entire matrix at once like this:
vector<vector<vector<double>>> matrix(10, vector<vector<double>>(10, vector<double>(10)));
This creates a complete 10x10x10 matrix. This ensures all indexes < 10 will be valid. I prefer this method. Then your function becomes:
double datawrite(int x, int y, int z, double val)
{
// Make sure indexes are valid
if (x >= matrix.size() || y >= matrix[x].size() || z >= matrix[x][y].size()) {
// Up to you what to do here.
// Throw an error or resize the matrix to fit the new data
}
// Store the value
matrix[x][y][z] = val;
return val;
}