C++Qt5.14.2版本不用UI形式绘制出频率响应曲线图和幅度响应曲线图

要绘制频率响应曲线和幅度响应曲线，可以使用Qt自带的QCustomPlot库。下面是一个简单的例子，展示如何在不使用UI的情况下使用QCustomPlot绘制频率响应曲线和幅度响应曲线：

#include <QApplication>
#include <QMainWindow>
#include "qcustomplot.h"

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    QMainWindow window;
    window.setWindowTitle("Frequency Response");

    // create plot widget
    QCustomPlot *plot = new QCustomPlot(&window);
    window.setCentralWidget(plot);

    // set plot title and axis labels
    plot->plotLayout()->insertRow(0);
    plot->plotLayout()->addElement(0, 0, new QCPTextElement(plot, "Frequency Response", QFont("sans", 12, QFont::Bold)));
    plot->xAxis->setLabel("Frequency");
    plot->yAxis->setLabel("Amplitude");

    // create data for frequency response curve
    QVector<double> frequency(1001), response(1001);
    for (int i = 0; i < 1001; i++)
    {
        frequency[i] = i / 10.0;
        response[i] = qSin(frequency[i] / 10.0) / (frequency[i] / 10.0);
    }

    // add frequency response curve to plot
    QCPGraph *freqResponse = plot->addGraph();
    freqResponse->setData(frequency, response);
    freqResponse->setPen(QPen(Qt::blue));

    // create data for amplitude response curve
    QVector<double> amplitude(101), dB(101);
    for (int i = 0; i < 101; i++)
    {
        amplitude[i] = i / 100.0;
        dB[i] = 20.0 * qLn(amplitude[i]) / qLn(10.0);
    }

    // add amplitude response curve to plot
    QCPGraph *ampResponse = plot->addGraph();
    ampResponse->setData(amplitude, dB);
    ampResponse->setPen(QPen(Qt::red));

    // set plot ranges and axes scales
    plot->xAxis->setRange(0, 100);
    plot->yAxis->setRange(-30, 10);
    plot->xAxis->setScaleType(QCPAxis::stLogarithmic);
    plot->yAxis->setScaleType(QCPAxis::stLogarithmic);
    plot->yAxis->setNumberFormat("eb");
    plot->yAxis->setNumberPrecision(0);

    // show the window
    window.show();

    return a.exec();
}

在这个例子中，我们创建了一个`QCustomPlot`对象，并将其设置为主窗口的中央部件。然后，我们设置了绘图的标题和坐标轴标签，并创建了用于绘制频率响应曲线和幅度响应曲线的数据。最后，我们将这些数据添加到绘图中，并设置了绘图的范围和刻度。运行程序后，您应该能够看到绘制的频率响应曲线和幅度响应曲线。