How do I write a moving Average to an array list class?

I'm trying to make an arraylist where I not only can I append(add) and insert, but also make a moving Average function in my arraylist class.

I've tried various research and examples online and I've officially hit a wall. I've also been having a problem with "capacity" where I get a scientific output or a 0 rather than an integer regarding the capacity in my resize() function. Can someone please help me fix my problem. I really need to get this fixed as soon as possible.

#ifndef ARRAYLIST_H_
#define ARRAYLIST_H_

#include<iostream>
using namespace std;

class arrayList{
    int size;
    int capacity;
    double *p;

void resize(){
    capacity *= 2; //THIS IS WHAT'S CRASHING THE CODE
    double *temp = new double[capacity];

    for(int i = 0; i < size; i++){
        temp[i] = p[i];
        delete []p;
        p = temp;
        temp = nullptr;
    }
}
public:
    arrayList(): size(0), capacity(1){
        p = new double[capacity];
    }

    arrayList(int cap): size(0), capacity(cap){
        p = new double[capacity];
    }

    //copy constructor
    arrayList(const arrayList& copy){
        size = copy.size;
        capacity = copy.capacity;
        p = new double[capacity];

        for(int i = 0; i < size; ++i)
            p[i] = copy.p[i];
    }

    //move constructor
    arrayList(arrayList&& move){
        size = move.size;
        capacity = move.capacity;
        p = move.p;

        move.size = 0;
        move.capacity = 0;
        move.p = nullptr;
    }

    //copy assignment operator
    arrayList& operator=(const arrayList& copyA){
        if (this != &copyA){
            size = copyA.size;
            capacity = copyA.capacity;
            p = new double[capacity];

        for(int i = 0; i < copyA.size; ++i)
            p[i] = copyA.p[i];
            delete []p;

        } return *this;
    }

    // move assignment operator
    arrayList& operator=(arrayList moveA){
        if (this != &moveA){
            size = moveA.size;
            capacity = moveA.capacity;
            delete []p;
            p = moveA.p;
            moveA.p = nullptr;
        } return *this;
    }

    //destructor
    ~arrayList(){
        delete []p;
    }

    void insert (int index, int value){
        if (index >= capacity){
            cout << "OUT OF BOUNDS!";
        }

        if(index < size && index >= 0){
            for (int i = size; i > index; --i){
                p[i] = p[i - 1];
            }
        p[index] = value;
        size++;
        } else{
            p[index] = value;
            size++;
        }
    }

    void append(int val){
        if (size == capacity)
            resize();
            p[size] = val;
            size++;
    }

    void movingAvg(const arrayList& avg, int kernel){
    // I REALLY NEED HELP WITH THIS PART.
    }

    friend ostream& operator<<(ostream& os, arrayList& val){
        for(int i = 0; i < val.size; ++i)
            os << val.p[i] << " ";
            os << endl << endl;

            return os;
    }
};

// main.cpp

int main(){

arrayList a;
a.append(45);
cout << a;

a.append(14);
cout << a;

a.insert(2, 76);
cout << a;

//CRASHES AT THIS POINT!

a.insert(3, 45);
cout << a;

a.insert(5, 23);
cout << a;

return 0;
}

OUTPUT:

45 

45 14 

45 14 76 0