How to read text file and draw line help.

[Ohmu11]

my data in text file like this
1.5
2.0
1.23
2.67

I would like to drawline vertical axis.Now i have no idea plz.
my code.

#include "dialog.h"
#include "ui_dialog.h"
#include<QPainter>
Dialog::Dialog(QWidget *parent) :
    QDialog(parent),
    ui(new Ui::Dialog)
 
{
 
    ui->setupUi(this);
   // bool w_flag = false;
}
 
Dialog::~Dialog()
{
 
    delete ui;
}
void Dialog::on_pushButton_2_clicked()
{
 
   m_fill = !m_fill;
   readfile();
   update();
 
}
 
void Dialog::paintEvent(QPaintEvent *e)
{
 
    QPainter painter(this);
    if(m_fill)
    {
       painter.setPen( QPen(Qt::red, 2,Qt::SolidLine) );
       painter.drawLine( 300, 300, 800,300);
    }
 
}
void Dialog::readfile()
{
    QString filename1 = "data.txt";//readfile
    QFile file1(filename1);
    file1.open(QIODevice::ReadOnly|QIODevice::Text);
    QTextStream in(&file1);
    QString init = in.readLine();
 
    file1.close();
}

#include "dialog.h"
#include "ui_dialog.h"
#include<QPainter>
Dialog::Dialog(QWidget *parent) :
    QDialog(parent),
    ui(new Ui::Dialog)

{

    ui->setupUi(this);
   // bool w_flag = false;
}

Dialog::~Dialog()
{

    delete ui;
}
void Dialog::on_pushButton_2_clicked()
{

   m_fill = !m_fill;
   readfile();
   update();

}

void Dialog::paintEvent(QPaintEvent *e)
{

    QPainter painter(this);
    if(m_fill)
    {
       painter.setPen( QPen(Qt::red, 2,Qt::SolidLine) );
       painter.drawLine( 300, 300, 800,300);
    }

}
void Dialog::readfile()
{
    QString filename1 = "data.txt";//readfile
    QFile file1(filename1);
    file1.open(QIODevice::ReadOnly|QIODevice::Text);
    QTextStream in(&file1);
    QString init = in.readLine();

    file1.close();
}

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[anda_skoa]

Well, you are drawing a horizontal line already, a vertical line is very similar: both points have the same x coordinates and different y coordinates.

Cheers,
_