graphing_japanese_age.cpp

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

#include "Graph.h"
#include "Window.h"

using namespace Graph_lib;
using namespace std;

struct Distribution {
    int year, young, middle, old;
};

istream& operator>>(istream& is, Distribution& d);

// data value to coordinate conversion
class Scale {
    int cbase;  // coordinate base
    int vbase;  // base of values
    double scale;

public:
    Scale(int b, int vb, double s) :cbase(b), vbase(vb), scale(s) {}
    int operator()(int v) const { return cbase + (v - vbase) * scale; }
};

// display Japanese age data read from a file
int main(int argc, char* argv[]) {
    if (argc < 2) {
        cout << "Usage: " << argv[0] << " input_file\n";
        return 0;
    }

    ifstream ifs(argv[1]);
    if (!ifs)
        error("can't open ", argv[1]);

    constexpr int xmax = 600;       // window size
    constexpr int ymax = 400;

    constexpr int xoffset = 100;    // distance from left-hand side of window to y axis
    constexpr int yoffset = 60;     // distance from bottom of window to x axis

    constexpr int xspace = 40;      // space beyond axis
    constexpr int yspace = 40;

    constexpr int xlength = xmax - xoffset - xspace;    // length of axes
    constexpr int ylength = ymax - yoffset - yspace;

    constexpr int base_year = 1960;
    constexpr int end_year = 2040;

    constexpr double xscale = double(xlength) / (end_year - base_year);
    constexpr double yscale = double(ylength) / 100;

    constexpr int font_size = 14;

    Scale xs(xoffset, base_year, xscale);
    Scale ys(ymax - yoffset, 0, -yscale);

    Graph_lib::Window win(Point(100, 100), xmax, ymax, "Aging Japan");

    Axis x_axis(
            Axis::x, Point(xoffset, ymax - yoffset), xlength, (end_year - base_year) / 10,
            "year  1960      1970      1980      1990      "
            "2000      2010      2020      2030      2040");
    x_axis.label.set_font_size(font_size);
    x_axis.label.move(-100, 0);

    Axis y_axis(Axis::y, Point(xoffset, ymax - yoffset), ylength, 10, "% of population");
    y_axis.label.set_font_size(font_size);

    Line current_year(Point(xs(2008), ys(0)), Point(xs(2008), ys(100)));
    current_year.set_style(Line_style::dash);

    Open_polyline children;
    Open_polyline adults;
    Open_polyline aged;

    for (Distribution d; ifs >> d;) {
        if (d.year < base_year || d.year > end_year)
            error("year out of range");
        if (d.young + d.middle + d.old != 100)
            error("percentages don't add up");
        const int x = xs(d.year);
        children.add(Point(x, ys(d.young)));
        adults.add(Point(x, ys(d.middle)));
        aged.add(Point(x, ys(d.old)));
    }

    Text children_label(Point(20, children.point(0).y), "age 0-14");
    children.set_color(Color::red);
    children_label.set_color(Color::red);
    children_label.set_font_size(font_size);

    Text adults_label(Point(20, adults.point(0).y), "age 15-64");
    adults.set_color(Color::blue);
    adults_label.set_color(Color::blue);
    adults_label.set_font_size(font_size);

    Text aged_label(Point(20, aged.point(0).y), "age 65+");
    aged.set_color(Color::dark_green);
    aged_label.set_color(Color::dark_green);
    aged_label.set_font_size(font_size);

    win.attach(x_axis);
    win.attach(y_axis);
    win.attach(current_year);

    win.attach(children);
    win.attach(adults);
    win.attach(aged);

    win.attach(children_label);
    win.attach(adults_label);
    win.attach(aged_label);

    gui_main();
    return 0;
}

// assume format: ( year : young middle old )
istream& operator>>(istream& is, Distribution& d) {
    char ch1 = 0, ch2 = 0, ch3 = 0;
    Distribution dd;

    if (!(is >> ch1 >> dd.year >> ch2 >> dd.young >> dd.middle >> dd.old >> ch3))
        return is;
    else if (ch1 != '(' || ch2 != ':' || ch3 != ')') {
        is.clear(ios_base::failbit);
        return is;
    }

    d = dd;
    return is;
}