Contour plot using customplot library with x, y, z data not coming full contour.

[Soniya]

I am using qt creator and trying to plot the contour plot with x, y, z data points. i am able to plot points but not contour. colormap is not coming. is there any interpolation required for it. is there any direct interpolation function for contour plot?
Below is the code
mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QVector>
#include "qcustomplot.h"
#include <QVBoxLayout>
#include <QFile>
#include <QTextStream>

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
Q_OBJECT

public:
MainWindow(QWidget *parent = nullptr);
~MainWindow();

protected:
void resizeEvent(QResizeEvent *event) override; // Override resizeEvent

private slots:

   void plotData();   // Function to plot data

private:
Ui::MainWindow *ui;
QCPColorScale *colorScale; // Pointer to color scale
QVector<QVector<double>> data; // Vector to hold the data
int nx; // Number of columns in data
int ny; // Number of rows in data
};

#endif // MAINWINDOW_H

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QFile>
#include <QTextStream>
#include <QVector>
#include <QDebug>
#include <QVBoxLayout>
#include <QHBoxLayout>

MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent), ui(new Ui::MainWindow)
{
ui->setupUi(this);

// Set up horizontal layout for the main window
ui->centralwidget = new QWidget(this);
ui->horizontalLayout = new QHBoxLayout(ui->centralwidget);
this->setCentralWidget(ui->centralwidget);

// Create and configure the custom plot
ui->customPlot = new QCustomPlot();
ui->customPlot->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
ui->horizontalLayout->addWidget(ui->customPlot); // Add custom plot to the layout

// Create color scale and add it to a layout
colorScale = new QCPColorScale(ui->customPlot);
colorScale->setType(QCPAxis::atRight);
ui->horizontalLayout ->addWidget(ui->customPlot); // Add color scale next to custom plot

//loadData(); // Load data on initialization
plotData(); // Now plot the data after loading

}

MainWindow::~MainWindow()
{
delete ui;
}

//void MainWindow::loadData()
//{
// data.resize(nx); // Resize data container to hold nx by ny values

// QFile file("D:\WorkData\2025\Projects\DRA\ContourPlotData\tecplot_ptt.dat");
// if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
// return;

// double x, y, z;
// int index = 0;
// QTextStream in(&file);

// while (!in.atEnd() && index < nx * ny) {
// QString line = in.readLine();
// QStringList numbers = line.split(' ', QString::SkipEmptyParts);

// if (numbers.size() == 3) {
// x = numbers[0].toDouble();
// y = numbers[1].toDouble();
// z = numbers[2].toDouble();

// int xIndex = static_cast<int>((x + 4) / (8.0 / (nx - 1)));
// int yIndex = static_cast<int>((y - 7) / (5.0 / (ny - 1)));

// if (xIndex >= 0 && xIndex < nx && yIndex >= 0 && yIndex < ny) {
// data[xIndex][yIndex] = z; // Store the z value in the data vector
// }
// index++;
// }
// }
// file.close();
//}

void MainWindow::resizeEvent(QResizeEvent *event)
{
QMainWindow::resizeEvent(event); // Call base class implementation

if (ui->customPlot) {
    // Ensure that the customPlot fills the main window
    ui->customPlot->setGeometry(0, 0, this->width(), this->height());
   ui->customPlot->replot(); // Optional: replot to ensure data is displayed correctly
}

}

void MainWindow::plotData()
{
QCPColorMap *colorMap = new QCPColorMap(ui->customPlot->xAxis, ui->customPlot->yAxis);
// Adjust dimensions as needed
int nx = 425;
int ny = 425;

    colorMap->data()->setSize(nx, ny); // Set the color map size
    colorMap->data()->setRange(QCPRange(-4, 4), QCPRange(7, 12)); // Modify based on your data range
    //colorMap->data()->setRange(QCPRange(-1.0, 1.0), QCPRange(7.5, 11.5));
    QFile file("D:\\WorkData\\2025\\Projects\\DRA\\ContourPlotData\\tecplot_ptt.dat");  // Assuming your data is saved in `data.txt`
    if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
        return;

    double x, y, z;
    int index = 0; // Cell index
    QTextStream in(&file);

    while (!in.atEnd() && index < nx * ny) {
        QString line = in.readLine();
        QStringList numbers = line.split(" ", QString::SkipEmptyParts);

        if (numbers.size() == 3) {
            // Convert the strings to double
            x = numbers[0].toDouble();
            y = numbers[1].toDouble();
            z = numbers[2].toDouble();

            // Find the index in the color map
            int xIndex = static_cast<int>((x - -4) / (8.0 / (nx - 1))); // Adjust based on your ranges
            int yIndex = static_cast<int>((y - 7) / (5.0 / (ny - 1))); // Adjust based on your ranges

            if (xIndex >= 0 && xIndex < nx && yIndex >= 0 && yIndex < ny) {
                colorMap->data()->setCell(xIndex, yIndex, z);
            }
            index++;
        }
    }
    file.close();

    // Setup color scale and appearance
    QCPColorScale *colorScale = new QCPColorScale(ui->customPlot);
    ui->customPlot->plotLayout()->addElement(0, 1, colorScale);
    colorScale->setType(QCPAxis::atRight);
    colorMap->setColorScale(colorScale);
    colorScale->axis()->setLabel("PTT"); // Z value label


    // Title setup
    //colorMap->setGradient(QCPColorGradient::gpJet); // Color gradient

   QCPColorGradient customGradient;
      customGradient.setColorStopAt(0, Qt::white); // Start color (white)
       customGradient.setColorStopAt(0.25, Qt::blue);   // End color (red)
      customGradient.setColorStopAt(0.5, Qt::cyan);
       customGradient.setColorStopAt(0.75, Qt::yellow);
       customGradient.setColorStopAt(1.0, Qt::red);   // End color (red)
       customGradient.setColorStopAt(1.25, Qt::darkGreen);
       customGradient.setColorStopAt(1.5, Qt::red);
       customGradient.setColorStopAt(1.75, Qt::darkRed);   // End color (red)



       colorMap->setGradient(customGradient); // Apply the custom gradient to the color map
       colorMap->rescaleDataRange(); // Rescale the color map to fit d

// QCPMarginGroup *marginGroup = new QCPMarginGroup(ui->customPlot);
// ui->customPlot->axisRect()->setMarginGroup(QCP::msBottom | QCP::msTop, marginGroup);
// colorScale->setMarginGroup(QCP::msBottom | QCP::msTop, marginGroup);
ui->customPlot->setWindowTitle("ContourPlot PTT"); // Set the main title

    // Axis titles setup
    ui->customPlot->xAxis->setLabel("X Axis Title"); // Set the label for X axis
    ui->customPlot->yAxis->setLabel("Y Axis Title"); // Set the label for Y axis
    //ui->customPlot->replot();
   // ui->customPlot->afterReplot();
   ui->horizontalLayout->addWidget(ui->customPlot);
    ui->customPlot->addLayer("contourLayer"); // Create a layer for contours
    colorMap->setLayer("contourLayer");
     ui->customPlot->rescaleAxes();

// QCPContourPlot *contourPlot = new QCPContourPlot(ui->customPlot);
// contourPlot->setColorMap(colorMap);
// contourPlot->setData(colorMap->data()); // Set data from the color map
// contourPlot->setContourFillColor(true); // This will fill the areas between contour lines
// contourPlot->setContourLines(15); // Set number of contour lines you want to display

}

mainwindow.ui

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
<class>MainWindow</class>
<widget class="QMainWindow" name="MainWindow">
<property name="geometry">
<rect>
<x>0</x>
<y>0</y>
<width>848</width>
<height>615</height>
</rect>
</property>
<property name="windowTitle">
<string>MainWindow</string>
</property>
<widget class="QWidget" name="centralwidget">
<widget class="QWidget" name="horizontalLayoutWidget">
<property name="geometry">
<rect>
<x>19</x>
<y>49</y>
<width>801</width>
<height>511</height>
</rect>
</property>
<layout class="QHBoxLayout" name="horizontalLayout">
<item>
<widget class="QCustomPlot" name="customPlot" native="true">
<property name="maximumSize">
<size>
<width>731</width>
<height>511</height>
</size>
</property>
</widget>
</item>
</layout>
</widget>
</widget>
<widget class="QMenuBar" name="menubar">
<property name="geometry">
<rect>
<x>0</x>
<y>0</y>
<width>848</width>
<height>26</height>
</rect>
</property>
</widget>
<widget class="QStatusBar" name="statusbar"/>
</widget>
<customwidgets>
<customwidget>
<class>QCustomPlot</class>
<extends>QWidget</extends>
<header location="global">qcustomplot.h</header>
<container>1</container>
</customwidget>
</customwidgets>
<resources/>
<connections/>
</ui>

main.cpp
#include "mainwindow.h"

#include <QApplication>

int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;
w.show();
return a.exec();
}

using qcustomplot.h and qcustomplot.cpp as well in same project.
can anyone please me to get contour plot

data is below
-1.3523 11.6294 1.6393
-1.2402 11.6441 1.5674
-1.1279 11.6576 1.6377
-1.0154 11.6698 1.7405
-0.9029 11.6807 1.7257
-0.7902 11.6904 1.7124
-0.6775 11.6987 1.6947
-0.5647 11.7058 1.6807
-0.4518 11.7115 1.6608
-0.3389 11.7160 1.6316
-0.2260 11.7193 1.5598
-0.1130 11.7212 1.6933
0.0000 11.7218 1.7488
0.1130 11.7212 1.7311
0.2260 11.7193 1.7134
0.3389 11.7160 1.6936
0.4518 11.7115 1.6768
0.5647 11.7058 1.6651

[jsulm]

@Soniya Please format your code properly. There is also no need to post commented out code if it has nothing to do with your issue.