#include "TGraph.h"
#include "TCanvas.h"

#include <stdlib.h>
#include <stdio.h>

static const double vref = 1.24;
static const double rd = 24;
static const double rv = 10;
static const double rdd = 8;
static const double rset = 39.9;

void plot (double vmax)
{
    double req = (vmax / vref - 1) / (1 / rd + 1 / rdd);
    double rt = 1 / (1 / req - 1 / rset - 1 / rv);
    
    printf("R_t = %.3e kOhm\n", rt);

    TGraph *g[5] = { new TGraph(),
		     new TGraph(),
		     new TGraph(),
		     new TGraph(),
		     new TGraph() };

    for (int i = 0; i < 256; ++i) {
	double r = i / 256.0 * rv + 60e-3;
	double _rd[5] = { 0.8 * rd, 0.9 * rd, rd, 1.1 * rd, 1.2 * rd };
	
	for (int j = 0; j < 5; ++j) {
	    double rd = 1 / (1 / _rd[j] + 1 / rdd);
	    double req = 1 / (1 / r + 1 / rt + 1 / rset);
	    double v = vref * (rd + req) / rd;
	    
	    g[j]->SetPoint(i, r, v);
	}
    }

    for (int i = 0; i < 5; ++i) {
	g[i]->SetLineWidth(2);
	g[i]->SetLineStyle(1 + abs(i - 2));
	g[i]->Draw(i ? "l" : "al");
	if (!i)
	    g[i]->GetXaxis()->SetTitle("R_{v} / k#Omega");
	    g[i]->GetYaxis()->SetTitle("V");
    }
    
    gPad->SetGridx();
    gPad->SetGridy();
}