void mkHist(char *filename)
{
  FILE *fp;
  fp = fopen(filename, "r");
  if (!fp) {
    fprintf(stderr, "cannot open %s\n", filename);
  }

  char buf[100];
  double data;
  TH1F *h1 = new TH1F("h1","Test",100, -1,1);

  while (1) {
    if (fgets(buf, sizeof(buf), fp) == NULL)
      break;
    if (buf[0] == '\n' || buf[0] == '#')
      continue;

    sscanf(buf, "%lf", &data);
    h1->Fill(data);
  }
  h1->Draw();
}