Reading data from csv file into an array

There are many, many errors in your program. Let me list up the most important:

• Usage of raw pointers for owned memory. Never do this in C++ (if at all, use std::unique_ptr instead)
• Do not use new in C++ to allocate memory (use std::make_unique)
• If you allocate memory with new, then you must delete it afterwards
• Best: Do use container from the standard library, in this case std::vector
• Always initialize all variables
• Always check the result of file operations like open or >>
• Handle errors
• Use ++v instead of v++
• Define variables, when you need them. Keep them scoped. Prevent Namespace pollution
• If you want to write C++ code, then use C++ language elements and not C
• Try to design your code with modern C++ language elements

So. I fixed your code, so that it runs, reads your example file and displays the result. I removed the major bugs. Please see:

#include <iostream>
#include <fstream>
#include <string>
#include <sstream>

float*** get3dArry(unsigned short widthX, unsigned short widthY, unsigned short widthZ) {
    unsigned short int i, j, x, y, z;
    float clvDefault = 0.0;

    float*** Cl = new float** [widthZ];
    for (i = 0; i < widthZ; i++)
    {
        Cl[i] = new float* [widthY];
        for (j = 0; j < widthY; j++)
        {
            Cl[i][j] = new float[widthX];
        }
    }

    std::ifstream clvIn;
    std::string clvFileName = "r:\\File_read.csv";
    clvIn.open(clvFileName.c_str());
    if (clvIn.fail())
    {
        std::cerr << "\n*** Error: Could not open input file\n";
    }
    else {
        std::string filejunk, line;
        char delim;
        //std::getline(clvIn, filejunk);
        int clvX, clvY, clvZ;
        float clvValue;

        for (z = 0; z < widthZ; z++)
        {
            for (y = 0; y < widthY; y++)
            {
                for (x = 0; x < widthX; x++)
                {
                    Cl[z][y][x] = clvDefault;
                }
            }
        }

        for (y = 0; (y < widthY) && std::getline(clvIn, line); ++y) {

            std::istringstream iss{ line };
            for (x = 0; (x < widthY) && (iss >> Cl[0][y][x]); ++x)
                ;
        }

        for (z = 0; z < widthZ; z++)
        {
            for (y = 0; y < widthY; y++)
            {
                for (x = 0; x < widthX; x++)
                {
                    Cl[z][y][x] = Cl[0][y][x];
                }
            }
        }
    }
    return Cl;
}

int main() {
    float*** a3d = get3dArry(4, 4, 3);

    for (int z = 0; z < 3; ++z) {
        std::cout << "\n";
        for (int y = 0; y < 4; ++y) {
            for (int x = 0; x < 4; ++x) {
                std::cout << a3d[z][y][x] << "\t";
            }
            std::cout << "\n";
            delete[] a3d[z][y];
        }
        delete[] a3d[z];
    }
    delete[] a3d;

    return 0;
}

However. I would not recommend to use that. The quality is too bad. It is error prone and somehow still complete a C-Program.

Please see the part, where I read the CSV file. Of course, there is no external library necessary. I hear often such nonesense recomendations for ultra simple CSV files. So, no library. Example from above code:

for (y = 0; (y < widthY) && std::getline(clvIn, line); ++y) {
    std::istringstream iss{ line };
    for (x = 0; (x < widthY) && (iss >> Cl[0][y][x]); ++x)
        ;
}

Nobody can persuade me, that I need a library, for what I can do with 3 simple lines of code.

If you are interested to learn, then I show you also a "more-modern" C++ solution:

#include <iostream>
#include <fstream>
#include <vector>
#include <string>
#include <sstream>
#include <iterator>

// Make reading datatypes easier
using DataType = float;
using Matrix1dX = std::vector<DataType>;
using Matrix2dYX = std::vector<Matrix1dX>;
using Matrix3dZYX = std::vector<Matrix2dYX>;

// This is the number of z values for the 3rd dimension. Whatever you want
constexpr size_t NumberOfDimensionZ = 3U;

int main() {

    // Open input csv file, and check, if open operation worked
    if (std::ifstream clvIn("r:\\File_read.csv"); clvIn) {

        // Define 2d array and initialize all values with 0.0;
        Matrix2dYX myx{};

        // Read all lines of the file and split values
        for (std::string line{}; std::getline(clvIn, line); ) {

            // Convert just read string to a std::istringstream
            std::istringstream iss{ line };

            // Add the new values to the 2d array. Iterate over all values in one line
            // then create a 1d vector inplace and add this line values to our 2d matrix
            myx.emplace_back(Matrix1dX(std::istream_iterator<DataType>(iss), {}));
        }
        // Define a 3d matrix, with a given size and having each z-value be the data from the csv file
        Matrix3dZYX mzyx(NumberOfDimensionZ, myx);


        // Some debug output
        // Show result to user
        for (const Matrix2dYX& m2 : mzyx) {
            std::cout << "\n";
            for (const Matrix1dX& m1 : m2) {
                for (const DataType& d : m1) std::cout << d << "\t";
                std::cout << "\n";
            }
        }
    }
    else {
        std::cerr << "\n*** Error: Could not open input file\n";
    }
    return 0;
}

Please note that you can write elegant very elegant and compact code in C++.

For reading the file and creating the 3d vector, I do not need any loop.

Please read and try to understand. Please google unknwon language constructs. If you do not understand, then ask.