# bar graph – group of people height data graphing [fltk]

Bjarne Stroustrup “Programming Principles and Practice Using C++”
Chapter 15 Exercise 8
Using GUI library called FLTK (Fast Light Tool Kit, “full tick”).

```Output:

```

[code language=”cpp”]
// Philipp Siedler
// Bjarne Stroustrup’s PP
// Chapter 15 Exercise 8

#define _USE_MATH_DEFINES
#include "Simple_window.h"
#include "Graph.h"
#include <cmath>

ostream& operator<<(ostream& out, Point& a) {
out << "(" << a.x << "," << a.y << ")";
return out;
}

// layout
constexpr int xmax = 600;
constexpr int ymax = 600;

constexpr int x_orig = xmax / 2;
constexpr int y_orig = ymax / 2;
Point orig(x_orig, y_orig);

constexpr int r_min = -10;
constexpr int r_max = 10;

constexpr int n_points = 400;

constexpr int x_scale = 2;
constexpr int y_scale = 2;

constexpr int xoffset = 100;
constexpr int yoffset = 100;

constexpr int xspace = 100;
constexpr int yspace = 100;

constexpr int xlength = xmax – xoffset – xspace;
constexpr int ylength = ymax – yoffset – yspace;

struct ppl_height
{
ppl_height(double height, int count)
:height(height), count(count) { }
double height;
int count;
};

void read_data(string location, vector<ppl_height>& v)
{
ifstream ist(location);
if (!ist) { error("no such file exists", location); }

char comma;
double height;
int count;

while (ist >> height >> comma >> count)
{
if (ist.eof()) {
break;
}
v.push_back(ppl_height(height, count));
}

}

class bar_graph : public Shape
{
public:
bar_graph(Point origin, vector<ppl_height>& data, int x_scale, int r1_min, int r1_max, int y_scale, int r2_min, int r2_max, int bar_width, Color col, string label);

void draw_lines() const;

vector<ppl_height>& get_data() { return data; }

private:
Point origin;
vector<ppl_height>& data;

int x_scale;
int r1_min;
int r1_max;

int y_scale;
int r2_min;
int r2_max;

int bar_width;

Color col;
string label;
};

bar_graph::bar_graph(Point origin, vector<ppl_height>& data, int x_scale, int r1_min, int r1_max, int y_scale, int r2_min, int r2_max, int bar_width, Color col, string label)
: origin(origin),
data(data),
x_scale(x_scale),
r1_min(r1_min),
r1_max(r1_max),
y_scale(y_scale),
r2_min(r2_min),
r2_max(r2_max),
bar_width(bar_width),
col(col),
label(label)
{

}

void bar_graph::draw_lines() const
{
int ds = data.size();

for (int i = 0; i < data.size(); i++) {

double w = double(bar_width / 2);
int h = data[i].height;
int c = data[i].count;

// scale factor
double sx = (xlength / 2.0) / (r1_max – r1_min);
double sy = (ylength / 2.0) / (r2_max – r2_min);

Point p0(origin.x + (h – r1_min) * sx – w, origin.y – c * sy);
Point p1(origin.x + (h – r1_min) * sx + w, origin.y);

Graph_lib::Rectangle r(p0, p1);

r.set_color(col);
r.set_fill_color(col);

r.draw();

// bar labels
string hl = to_string((int)data[i].height);
Text height_label(Point(p1.x – bar_width, p1.y + 15), hl);
height_label.set_color(col);
height_label.draw();

string cl = to_string((int)data[i].count);
Text count_label(Point(p0.x, p0.y – 10), cl);
count_label.set_color(col);
count_label.draw();

}

// graph label
Text gl(Point(origin.x – 70, origin.y + 15), label);
gl.set_color(col);

gl.draw();
}

int main()
try
{
Point tl(100, 100);
Simple_window win(tl, xmax, ymax, "Function graphs.");

int r1_min = 160;
int r1_max = 200;

int r2_min = 5;
int r2_max = 30;

int bar_width = 15;

// notch label x
string x_notch = "1 == " + to_string((r1_max – r1_min) / 10);

// notch label y
ostringstream strs;
strs << setprecision(2) << (r2_max – r2_min) / 10.0;
string y_notch = "1 == " + strs.str();

// x axis
Axis x(Axis::x, Point(orig.x – 200, orig.y), 400, 20, x_notch);
x.set_color(Color::black);
win.attach(x);

// y axis
Axis y(Axis::y, Point(orig.x, orig.y + 200), 400, 20, y_notch);
y.set_color(Color::black);
win.attach(y);

// people height data
vector<ppl_height> d = { ppl_height(170, 7),
ppl_height(175, 9),
ppl_height(180, 23),
ppl_height(185, 17),
ppl_height(190, 6),
ppl_height(195, 1)
};

// stream data from file
vector<ppl_height> dff;
string location = "input/height_data.txt";

// bar graph
bar_graph bg(orig, dff, x_scale, r1_min, r1_max, y_scale, r2_min, r2_max, bar_width, Color::blue, "bar graph");
win.attach(bg);

win.wait_for_button();
keep_window_open();
}
catch (exception& e) {
cerr << "error: " << e.what() << ‘\n’;
keep_window_open();
return 1;
}

catch (…) {
cerr << "Unknown exception!\n";
keep_window_open();
return 2;
}
[/code]