Read data and add it to a chart

[deleted286]

Hi everyone. Here is a code script that can write and read data from txt and show it on display in a time interval. I want to convert the screen in a real time chart. I want to add my datas to chart in real time. For example, read data in 0,2 sec and add chart in an order. How can i do such thing?

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QFile>
#include <QTextStream>
#include <QMessageBox>
#include <QTimer>
#include <QList>
#include <qlist.h>
#include <QDebug>

 QTimer *timer = new QTimer();


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


    connect(timer, SIGNAL(timeout()), SLOT(Timer_Slot()));

}

void MainWindow::Timer_Slot() {

    QString line = allLines[curIndex];
    ui->plainTextEdit->setPlainText(line);
    if (curIndex < allLines.size() - 1 ) {
          curIndex++;
      }

}


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


void MainWindow::on_pushButton_2_clicked()  //write
{
    QFile file("C:/Users/ilknu/Documents/QFileDemo/abc.txt");
    if(!file.open(QFile::WriteOnly | QFile::Text )) {

        QMessageBox::warning(this, "title", "file not open");


    }

    QTextStream out (&file);
    QString text = ui->plainTextEdit->toPlainText();
    out << text;
    file.flush();
    file.close();


}

void MainWindow::on_pushButton_clicked()  //read
{

    QFile file("C:/Users/ilknu/Documents/QFileDemo/abc.txt");

  if(file.open(QIODevice::ReadOnly)) {
      QTextStream in (&file);
      while (!in.atEnd()) {
          QString line = in.readLine();
          allLines.append(line);
      }

  file.close();

}

  file.close();
  curIndex=0;
  timer->start(200);
}

[jsulm]

@suslucoder From where do you want to read the data?

[deleted286]

@jsulm i want to read from txt

[jsulm]

@suslucoder Then I'm not sure what exactly you want to do. What do you mean by "real time"? You can simply read the whole file at once and update the chart.

[deleted286]

@jsulm I don't want it to read all the data and add it to the chart. It can read the entire file in once, but I want it to add the data to the chart every 0.2 seconds. It should always proceed by adding the most recently read data to the chart

[jsulm]

@suslucoder said in Read data and add it to a chart:

but I want it to add the data to the chart every 0.2 seconds

Then this is not "realtime".
You already have the file content in allLines and you already have Timer_Slot() slot. So, what prevents you from adding next data line to your chart in that slot?

[deleted286]

@jsulm I dont know how to do it, that is the reason I asked for help

[jsulm]

@suslucoder There are many examples: https://doc.qt.io/qt-5/qtcharts-examples.html
Take time to see how data is added to a chart.

[deleted286]

@jsulm as you said, I already have the file content in allLines. When i do series.append(allLines) to adding chart I get an error. Thank you I will analyze the examples

[jsulm]

@suslucoder I told you in that other thread from you that you can't use a string list there. Please also read documentation...

[JonB]

@suslucoder
@jsulm already answered this last question in https://forum.qt.io/topic/122320/how-can-i-add-txt-file-datas-in-qlineseries/2. You cannot add a a string (or string list) to a chart, you have to parse it to generate the actual desired numbers.

For adding data every few seconds: whether you read the lines from the file as you go or you read them all into a list in memory, either way on a QTimer::timeout() signal read the next however-many from the file/list and add them to the chart.

[deleted286]

@JonB Okey. I understand. I should use another struct instead of string list, right?

[JonB]

@suslucoder
Well it's not another "struct". You presumably have a file containing the text of numbers, perhaps separated by commas or new lines or something. You need to convert those to X,Y numeric values, and then pass those (or QPointFs) to add to the chart series. It doesn't matter whether you do that at the time of reading in the file or just before adding them to the series, but you will need to do so at one of those two stages.

[jsulm]

@suslucoder said in Read data and add it to a chart:

I should use another struct instead of string list, right?

You should use what the method to set the data expects. That's why I suggested to read the documentation: it is documented quite clearly.

[deleted286]

@jsulm ıs there any example that doing exactly what you said?

[jsulm]

@suslucoder I already posted a link to charts examples.
For example: https://doc.qt.io/qt-5/qtcharts-temperaturerecords-example.html
And you still did not tell us what data you actually want to show and what type of chart you need...

[mrjj]

Hi
Please show one line from the "C:/Users/ilknu/Documents/QFileDemo/abc.txt"
so we know how data is. else it's impossible to give any hints on how you can show that in a chart.

[deleted286]

@mrjj Here it is

1991 01 213.5 136.9 0.64 220.5 147.6 229.4 205.5 8 17.4
1991 02 270.2 167.5 0.62 221.5 147.6 243.0 206.3 10 18.4

[JonB]

@suslucoder

QString line = read_one_line_from_file();
QStringList list = line.split(QLatin1Char(' '), Qt::SkipEmptyParts);
for (const QString &entry : list)
{
    double num = entry.toDouble();    // or `unsigned num = entry.toUInt()` for the first 2 numbers on each line, by the look of it
    // do whatever is necessary with each `double` number retrieved
    // such as adding pairs directly to the chart, or building a `QLineSeries`, or whatever
}

[deleted286]

@JonB Thank you. Where should I place the code script?