void MainWindow::readcsvfile() //讀取csv
{
 QFile csvFile("C:/Users/Administrator/Desktop/Demo/0702.CSV");
 QStringList csvList;
 csvList.clear();
 if (csvFile.open(QIODevice::ReadWrite)) //對csv檔案進行讀寫操作
 {
  QTextStream stream(&csvFile);
  while (!stream.atEnd())
 {
 csvList.push_back(stream.readLine()); //儲存到List當中
 }
 csvFile.close();
 }
 else
 {
	 QMessageBox::about(NULL, "csv檔案", "未開啟該檔案！");
 }
   int i = 0;
   Q_FOREACH(QString str, csvList)   //遍歷List
  {
   i = i + 1;
   QStringList valsplit = str.split(","); //分隔字串
   if(i > 2)
   {
    //得到深度、聲速、溫度
    QString depth = valsplit[0];
    QString sonicvelocity = valsplit[1];
    QString temperature = valsplit[2];
    double depthvalue = depth.toDouble();
    double sonicvalue = sonicvelocity.toDouble();
    double tempvalue = temperature.toDouble();
	//Q//MessageBox::warning(NULL, "dd", QString::number(tempvalue));
	QPointF point;
    point.setX(depthvalue);
    point.setY(sonicvalue);
	QPointF point2;
	point2.setX(depthvalue);
	point2.setY(tempvalue + 1510);
    vectors.append(point);
	vector2.append(point2);
   }
  }
}

void MainWindow::lineChart() //繪製圖
{
    //設定X,Y標題
    ui->qwtPlot->setAxisTitle(QwtPlot::xBottom, QString::fromLocal8Bit("深度(m)"));
    ui->qwtPlot->setAxisTitle(QwtPlot::yLeft, QString::fromLocal8Bit("聲速(m/s)"));
    ui->qwtPlot->setAxisTitle(QwtPlot::yRight, QString::fromLocal8Bit("溫度(°C)"));
    ui->qwtPlot->enableAxis(QwtPlot::yRight,true);
    ui->qwtPlot->setAxisScale(QwtPlot::yLeft,1538,1540,0.2);
    ui->qwtPlot->setAxisScale(QwtPlot::xBottom,0,30,2);
    ui->qwtPlot->setAxisScale(QwtPlot::yRight,28,30,0.2);

	//ui->qwtPlot->set
    //構造麴線資料
     QwtPointSeriesData* series = new QwtPointSeriesData(vectors);
	 //設定網格
	 QwtPlotGrid* grid = new QwtPlotGrid();
	 grid->setPen(QColor(222, 222, 222), 1);
	 grid->attach(ui->qwtPlot);
	 //create plot item
     QwtPlotCurve* curve1 = new QwtPlotCurve(QString::fromLocal8Bit("聲速"));
     //設定資料
	 curve1->setData(series);
	 //設定畫筆顏色==就是影象顏色
	 curve1->setPen(QColor(255, 0, 0), 2, Qt::SolidLine);
	 //使曲線更光滑
	 curve1->setCurveAttribute(QwtPlotCurve::Fitted, true);
	 //把曲線附加到qwtPlot上
     curve1->attach(ui->qwtPlot);
     //新增溫度-深度曲線
	 //構造麴線資料
	 QwtPointSeriesData* series2 = new QwtPointSeriesData(vector2);
	 //create plot item
	 QwtPlotCurve* curve2 = new QwtPlotCurve(QString::fromLocal8Bit("溫度"));
	 //設定資料
	 curve2->setData(series2);
	 //設定畫筆顏色=影象顏色
	 curve2->setPen(QColor(127, 222, 335), 2, Qt::SolidLine);
	 //使曲線更光滑
	 curve2->setCurveAttribute(QwtPlotCurve::Fitted, true);
	 //把曲線附加到qwtPlot上
	 curve2->attach(ui->qwtPlot);

	 //設定圖例
	 QwtLegend *legend = new QwtLegend;
	 legend->setDefaultItemMode(QwtLegendData::ReadOnly);
	 ui->qwtPlot->insertLegend(legend,QwtPlot::BottomLegend);//插入圖例
	 ui->qwtPlot->replot();
     ui->qwtPlot->show();
}
 

需要第三方庫QWT