Little help with a project

FelpsGK

Hello guys. I'm Brazilian and I'm learning QT. I want to make a simple project, but I'm having trouble developing the code. The idea is to create a method that does a sin (sin () math function) that receives as a parameter another method that increments from 1 to -1, with steps of 0.1. The first method will output an array that I would use to fill a chart. Someone help me? please..

VRonin

@FelpsGK said in Little help with a project:

The idea is to create a method that does a sin (sin () math function)

std::sin

that increments from 1 to -1, with steps of 0.1

for(double i = 1.0; i>=-1.0; i-=0.1)

The first method will output an array

QVector<double> array;
array.reserve(20);
for(double i = 1.0; i>=-1.0; i-=0.1)
array << std::sin(i);

FelpsGK

@VRonin I think I said it wrong. As a method, I mentioned the function. Something like "public void ....". I usually program in java, so I'm used to calling everything by method. But I understood logic. The question would be, how to fill a graph with this array? Make the graph receive the data and auto-fill it from the received array.

VRonin

As a method, I mentioned the function.

std::sin is already a function. I don't see the advantage of having a function doing what a for loop does

From https://doc.qt.io/qt-5/qtcharts-linechart-example.html

#include <QtWidgets/QApplication>
#include <QtWidgets/QMainWindow>
#include <QtCharts/QChartView>
#include <QtCharts/QLineSeries>

QT_CHARTS_USE_NAMESPACE

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
const double doublePi = 2.0*std::acos(-1);
    QLineSeries *series = new QLineSeries();
for(double i = 0; i>=doublePi ; i+=0.1)
series->append(i,  std::sin(i););

    QChart *chart = new QChart();
    chart->legend()->hide();
    chart->addSeries(series);
    chart->createDefaultAxes();
    chart->setTitle("Sin chart example");

    QChartView *chartView = new QChartView(chart);
    chartView->setRenderHint(QPainter::Antialiasing);

    QMainWindow window;
    window.setCentralWidget(chartView);
    window.resize(400, 300);
    window.show();

    return a.exec();
}

FelpsGK

@VRonin
I'm very lazy and slow on this. So one last question: If I copy this code there in my respective class, it already works? Or am I going to need to do something?

FelpsGK

The graph is showing nothing

6thC

Kinda comes across as "do my job for me".
You are a developer, it's your job to read the documentation on Charts if you want charts... at least try.

https://doc.qt.io/qt-5.9/qtcharts-index.html

To link against the Qt Charts module, add this line to your qmake project file:
QT += charts

I cannot find a reference to but seem to remember also needing:
widgets
Maybe because I use ChartView's? Dunno.

QT_CHARTS_USE_NAMESPACE
is a macro and does the same as this, I can't really remember, but again, the docs say and how I now use is as per docs:

If you intend to use Qt Charts C++ classes in your application, use the following include and using directives:
#include <QtCharts>
using namespace QtCharts;

You won't (or shouldn't imo) get far being that kind of lazy. Nobody appreciates carrying another developer, we have enough to do already.