function extract_suishitsu_data(dt) {    // 水質データの抽出
    const date = new Date(dt);
    const year = date.getFullYear();
    const month = date.getMonth() + 1;
    const day = date.getDate();
    const hour = date.getHours();
    const minute = date.getMinutes();
    for(var i = 0; i < a_suishitsu.length; i++) {
        for(var j = 0; j < a_suishitsu[i].length; j++) {
            var a = a_suishitsu[i][j].split(",");
            if(a.length < 16) continue;
            var date2 = new Date(a[0] + " " + a[1]);
            if(date2.getTime() < date.getTime()) {
                suishitsu[i] = a;
            } else {
                break;
            }
        }
    }
}

function extract_data_column(data, num, dt, st) {
// 配列dataの中から測定時刻dtのnum列目の値を取り出す
  const date = new Date(dt);
  /*
  const year = date.getFullYear();
  const month = date.getMonth() + 1;
  const day = date.getDate();
  const hour = date.getHours();
  const minute = date.getMinutes();
  */

  for(var j = st; j >= 0; j--) {
    var a = data[j].split(",");
    //if(a.length < 16) continue;
    var date2 = new Date(a[0] + " " + a[1]);
    if(date2.getTime() < date.getTime()) {
      if(date2.getTime() < (date.getTime() - 1000 * 60 * 30)) {
        st_buf = j;
        break;
      }
      if(a[num] == "Err") return -1;
      st_buf = j;
      return a[num];
    } else {
      continue;
    }
  }
  return -1;
}