chapter 20.6绘制数据图

2.JPG 1.png

#include "Graph.h"
#include "Simple_window.h"
struct Distribution {
    int year, young, middle, old;
};
// data format ( year : young middle old )
istream& operator>>(istream& is, Distribution& d)
{
    char ch1 = 0;
    char ch2 = 0;
    char ch3 = 0;
    Distribution dd;

    if (is >> ch1 >> dd.year
        >> ch2 >> dd.young >> dd.middle >> dd.old
        >> ch3) {
        if (ch1 != '(' || ch2 != ':' || ch3 != ')') {
            is.clear(ios_base::failbit);
            return is;
        }
    }
    else
        return is;
    d = dd;
    return is;
}
class Scale {                // data value to coordinate conversion
    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; }
};
int main(){
    const int xmax = 600;    // window size
    const int ymax = 400;

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

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

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

    const int base_year = 1960;
    const int end_year = 2040;

    const double xscale
        = double(xlength) / (end_year - base_year); // scale of x values
    const double yscale = double(ylength) / 100;  // scale of y values 

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

    string file_name = "D:/Workspace/cpp/Projects/data.txt";
    ifstream ifs(file_name.c_str());
    if (!ifs) error("can't open ", file_name);
    cout << "open file success!\n";

    Open_polyline children;
    Open_polyline adults;
    Open_polyline aged;

    Distribution d;
    while (ifs >> d) {
        if (d.year < base_year || end_year < d.year) error("year out of range");
        if (d.young + d.middle + d.old != 100) error("percentages don't add up");
        int x = xs(d.year);//page 157 is wrong!
        children.add(Point(x, ys(d.young)));
        adults.add(Point(x, ys(d.middle)));
        aged.add(Point(x, ys(d.old)));
    }
    Simple_window win(Point(100, 100), xmax, ymax, "Aging Japan");

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

    Axis y(Axis::y, Point(xoffset, ymax - yoffset), ylength, 10, "% of population");
    y.set_color(Color::blue);

    Line current_year(Point(xs(2004), ys(0)), Point(xs(2004), ys(100)));
    current_year.set_color(Color::dark_green);
    current_year.set_style(Line_style::dash);

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

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

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

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

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

    win.attach(x);
    win.attach(y);
    win.attach(current_year);
    win.wait_for_button();
}