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Source code

void PlottingGraph::draw()
{
	m_time++;
	memmove(m_y, &m_y[1], 99 * sizeof(double));
	m_y[99] =  10 * sin((double)m_time / 360 * 3.1415 * 10) + rand() % 4000 -2000;

	for (int i = 0; i < 100; i++)
            m_x[i]++;
	if (!m_curve)
	{      
       	        m_curve = new QwtPlotCurve();
                m_curve->setPen(QPen(Qt::red));
                m_curve->setData(m_x, m_y, 100);
	        m_curve->attach(myPlot);
	}
    m_curve->setData(m_x, m_y,100);
    myPlot->setAxisScale(QwtPlot::xBottom, m_time, m_time +100); 
}

Source code

m_y[99] =  10 * sin((double)m_time / 360 * 3.1415 * 10) + rand() % 4000 -2000;

Source code

#include <QSqlQuery>
#include <QMenu>
plot_db::plot_db(QWidget *parent)
: QMainWindow(parent)
, m_curve(0)
{
ui.setupUi(this);
QTimer *timer = new QTimer(this);
connect(timer, SIGNAL(timeout()), this, SLOT(draw()));

timer->start(1000);
myPlot->setTitle("Pressure ");
myPlot->setAxisTitle(QwtPlot::xBottom, " System time [h:m:s]");
myPlot->setAxisScale(QwtPlot::xBottom, 0,60 );
myPlot->setAxisTitle(QwtPlot::yLeft, "Degree");
myPlot->setAxisScale(QwtPlot::yLeft, -60,60 );
myPlot->setAutoReplot(true);

}

plot_db::~plot_db()
{

}

void plot_db::draw()
{
QSqlQuery q;
if( q.exec( "select s_x, s_y from data_table order by x;" ) )
{
nb = q.size();
s_x = new double[nb];
s_y = new double[nb];

for( int i = 0; q.size(); i++ )
{
s_x[i] = q.value(0).toDouble();
s_y[i] = q.value(0).toDouble();
}
}
m_curve = new QwtPlotCurve();
m_curve->setPen(QPen(Qt::red));
m_curve->setData(s_x, s_y, 100);
m_curve->attach(myPlot);
}

Source code

#include "qwt_plot.h"
#include <qwt_plot_curve.h>

using namespace Ui;
class plot_db : public QMainWindow, public plot_dbClass
{
Q_OBJECT

public:
plot_db(QWidget *parent = 0);
~plot_db();

private slots:

void draw();

private:
int nb;
QwtPlotCurve *m_curve;
double s_x[100];
double s_y[100];
Ui::plot_dbClass ui;
};

Source code

#ifndef CONNECTION_H
#define CONNECTION_H

#include <QtGui/QMainWindow>
#include <QtSql>
#include <QMessageBox>
#include <QTableView>


inline bool createConnection()
{
QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
db.setDatabaseName(" Plot_DB ");
if (!db.open()) 
{
QMessageBox::critical(0, qApp->tr("Cannot open database"), 
qApp->tr("Unable to establish a database connection.\n"
"This example needs SQLite support. Please read "
"the Qt SQL driver documentation for information how "
"to build it.\n\n"
"Click Cancel to exit."), QMessageBox::Cancel);
return false;
}
QSqlQuery query;

if (!query.exec("create table if not exists data_table(s_x varchar(20) primary key, "
"s_y varchar(20))"))
{
QMessageBox::critical(0, "Failed", "Failed create Te table");
return false;
}
query.exec("insert into data_table values(0,-60 )");
query.exec("insert into Acquisition values(10, 0)");
query.exec("insert into Acquisition values(20, 40)");
query.exec("insert into Acquisition values(28, 0)");
query.exec("insert into Acquisition values(30, -30)");
query.exec("insert into Acquisition values(38, 0)");
query.exec("insert into Acquisition values(40, 38 )");
query.exec("insert into Acquisition values(50, 0 )");
query.exec("insert into Acquisition values(52,-30 )");
query.exec("insert into Acquisition values(55, 0)");
query.exec("insert into Acquisition values(60,50)");
return true;
}
#endif

Source code

.\plot_db.cpp(44) : error C2440: '=' : cannot convert from 'double *' to 'double [100]'
There are no conversions to array types, although there are conversions to references or pointers to arrays
.\plot_db.cpp(45) : error C2440: '=' : cannot convert from 'double *' to 'double [100]'
There are no conversions to array types, although there are conversions to references or pointers to arrays
main.cpp

Source code

/* *****************test_plotdb.cpp****************** */


m_sqlModel = new QSqlQueryModel(this);
QSqlQuery q("SELECT xval,yval FROM data_table1");
if (q.exec())
{
        for(int i=q.first();i<q.last();i++) 
{
*s_x=q.value(0).toDouble();
*s_y=q.value(1).toDouble();
m_curve = new QwtPlotCurve();
m_curve->setPen(QPen(Qt::red));
m_curve->setData((const double*)s_x, (const double*)s_y, 100);
//m_curve->setRawData(s_x,s_y,Size);
m_curve->attach(myPlot);
myPlot->replot();
}
}
else
{
QMessageBox::critical(this, "Failure", "Query failure");
}

Source code

/* *****************test_plotdb.h****************** */
 

class test_plotdb : public QDialog,public Ui::test_plotdbClass
{
	Q_OBJECT

public:
	test_plotdb(QWidget *parent = 0);
	~test_plotdb();

private slots:
	void draw();
//	Ui::test_plotdbClass ui;
private:
	QwtPlotCurve *m_curve;
	QSqlQueryModel *m_sqlModel;
	int nb;
	double *s_x;
	double *s_y;

private slots:
	void on_plotButton_clicked();
};