MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent),
    ui(new Ui::MainWindow)
{    
    ui->setupUi (this);
    ui->myPlot->setTitle (QString::fromLocal8Bit ("Графики"));

    grid = new QwtPlotGrid;
    grid->enableXMin (true);
    grid->enableYMin (true);

    grid->setMajPen (QPen(Qt::black,0,Qt::DotLine));
    grid->setMinPen (QPen(Qt::gray,0,Qt::DotLine));
    grid->attach (ui->myPlot);

    ui->myPlot->canvas ()->setCursor (Qt::ArrowCursor);

    curv1 = new QwtPlotCurve(QString::fromLocal8Bit("exp(x)"));
    curv1->setRenderHint(QwtPlotItem::RenderAntialiased);
    curv1->setPen(QPen(Qt::red));

    symbol1 = new QwtSymbol();
    symbol1->setStyle (QwtSymbol::Ellipse);
    symbol1->setPen (QColor(Qt::black));
    symbol1->setSize (5);
    curv1->setSymbol (symbol1);

    curv2 = new QwtPlotCurve(QString::fromLocal8Bit ("X*X+3X"));
    curv2->setRenderHint (QwtPlotItem::RenderAntialiased);
    curv2->setPen (QPen(Qt::green));

    symbol2 = new QwtSymbol();
    symbol2->setStyle (QwtSymbol::Rect);
    symbol2->setPen (QColor(Qt::blue));
    symbol2->setSize (5);
    curv2->setSymbol (symbol2);

    leg = new QwtLegend();
    leg->setItemMode(QwtLegend::ReadOnlyItem);
    ui->myPlot->insertLegend(leg,QwtPlot::TopLegend);

    plot_fat();

    ui->myPlot->replot ();

}

void MainWindow::plot_fat ()
{
    const int N = 13;
    int n;
    int numberCurve;   
    
    double x[N+1]={1,2,3,6,8,9,11,12,13,14,18,21,22};
    //double x[N+1]={-10,-7,-6,-5,-4, -2,-1,0, 2,3,6,9,10};
    double y[N+1];
    double x2[N+1];
    double y2[N+1];
    double AxisXmax = 0;
    double AxisXmin = 0;
    double AxisYmax = 0;
    double AxisYmin = 0;
    double errorX;
    for(int k = 0; k < N; k++ )
    {

    y[k]=exp(x[k]); //первый график

    x2[k]= x[k]+ 2;
    y2[k]=x2[k]*x[k] + 3 * x2[k];  //exp(x2[k]); //второй график

//определяем минимум макимум х и у
    if(x[k] > AxisXmax) AxisXmax = x[k]; 

    if(x[k] < AxisXmin) AxisXmin = x[k];

    if(y[k] < AxisYmin) AxisYmin = y[k];

    if(y[k] > AxisYmax) AxisYmax = y[k];  

    if(x[k] < 0 ) errorX = x[k];
    }

    numberCurve = 1;

    n = plot_first(AxisXmax,AxisXmin,AxisYmax,AxisYmin,errorX,x,y,N,numberCurve);
    if( n == 0 )
    {
        numberCurve++;
        for(int k=0; k < N; k++)
        {
        x[k]=x2[k];
        y[k]=y2[k];
        }
        n = plot_next(x,y,N,numberCurve);
    }

}

int MainWindow::plot_first (double AxisXmax, double AxisXmin, double AxisYmax, double AxisYmin, double errorX, double *x, double *y, const int N, int numberCurve)
{
////опре деление в каких осях рисовать в логарифмических или линейных
    //qDebug("1 i = %i", i);

    if(!ui->Log10X->isChecked () && !ui->Log10Y->isChecked ())
    {
        if(i == 1)
        {
            ui->myPlot->setAxisScaleEngine (QwtPlot::yLeft, new QwtLog10ScaleEngine);
            ui->myPlot->setAxisScaleEngine (QwtPlot::xBottom, new QwtLog10ScaleEngine);
            ui->Log10X->setChecked (true);
            ui->Log10Y->setChecked (true);
            AxisYmin=1;
            AxisXmin=1;
            if(errorX<0)
            {
                QMessageBox::warning (this,tr("Warning"),tr("There are negative values"));
            }
        }
        if(i == 2)
        {
            ui->myPlot->setAxisScaleEngine (QwtPlot::yLeft, new QwtLinearScaleEngine);
            ui->myPlot->setAxisScaleEngine (QwtPlot::xBottom, new QwtLinearScaleEngine);
        }
    }else
    {
        if(ui->Log10X->isChecked ()) AxisXmin=0.1;
        if(ui->Log10Y->isChecked ()) AxisYmin=0.1;
    }

    ui->myPlot->setAxisTitle(
        QwtPlot::xBottom,QString::fromLocal8Bit("X"));
    ui->myPlot->setAxisScale(QwtPlot::xBottom, AxisXmin, AxisXmax);

    ui->myPlot->setAxisTitle(
        QwtPlot::yLeft,QString::fromLocal8Bit("Y"));
    ui->myPlot->setAxisScale(QwtPlot::yLeft, AxisYmin, AxisYmax);

    showData(x,y,N,numberCurve);

    ui->myPlot->replot ();
    return 0;
}

int MainWindow::plot_next (double *x, double *y, const int N, int numberCurve)
{
    showData(x,y,N, numberCurve);
    ui->myPlot->replot ();
    return 1;
}