Selecting a circular region in 2D scatter plot

[BKn]

I have a 2D scatter plot.
Now I want to select a circular region in this plot and use the data inside the circular region for further analysis.
Is there any way to do that in C++?

Thanks in advance

[tpb]

#include <iostream>
#include <iomanip>
#include <vector>
#include <random>
using namespace std;

namespace Rnd {
    random_device rd;
    default_random_engine eng(rd());
    // return random integer from 0 to high-1
    int n(int high) { return eng() % high; }
    // return random double from 0.0 to 1.0
    double flt() { return eng() / (double)eng.max(); }
};

struct Point {
    double x, y;
    // Construct with x and y from -1.0 to 1.0.
    Point() : x(Rnd::flt()*2-1), y(Rnd::flt()*2-1) {}
    Point(double x, double y) : x(x), y(y) {}
};

ostream& operator<<(ostream& os, Point& p) {
    return os << setw(8) << p.x << ' '  << setw(8) << p.y;
}

vector<Point> inCircle(vector<Point>& v, Point center, double radius) {
    vector<Point> w;
    radius *= radius;
    for (auto o: v) {
        double x = o.x - center.x;
        double y = o.y - center.y;
        if (x * x + y * y <= radius)
            w.push_back(o);
    }
    return w;
}

int main() {
    vector<Point> v;
    for (int i = 0; i < 100; i++)
        v.push_back(Point());
    cout << fixed << setprecision(3);
    for (auto o: v)
        cout << o << '\n';
    vector<Point> w = inCircle(v, Point(.5, .5), .5);
    cout << "\n\n";
    for (auto o: w)
        cout << o << '\n';
}