How can I make “real-time” plots with wxMathPlot?

问题:

I am thinking of using wxMathPlot for plotting/graphing some data that arrives continuously. I want to draw "Real-time" plot/graph using it. Is that possible?

I.E. I don't want just a static graph of a one-time read of a file - I want the streaming data plotted and continued out to the right of the graph - (and let the left side fall off/scroll out of view)

EDIT

I still have not gotten an answer for this. There is an interesting class in the wxmathPlot library called mpFXYVector but that appears just to draw one plot from a vector of data. What I want is something that can be fed a stream and scroll the graph horizontally (and also resize the scale if needed)

回答1:

I think mpFXYVector is the way to go.

The simplest way to deal with this might be to write a wrapper class for mpFXYVector which holds a FIFO buffer of recent data points. Each time a new datapoint arrives, add it to the FIFO buffer, which will drop the oldest point, then load mpFXYVector with the updated buffer. The wxMathPlot class mpWindow will look after the rest of what you need.

A more elegant approach would be a specialization of mpFXYVector which implements the FIFO buffer, using the simple vectors in mpFXYVector. The advantage of this would be that you are holding just one copy of the display data. Unless you are displaying many thousands of points, I doubt the advantage is worth the extra trouble of inheriting from mpFXYVector, rather than simply using the mpFXYVector documented interface.

After looking at the details, the only tricky bit is to replace mpFXYVector::SetData() with a new method Add() to add data points as they arrive. The new method needs to manage the mpFXYVector vectors as FIFO buffers, and to re-implement the code to update the bounding box ( which unfortunately was not written with inheritance in mind ).

The result is that specialization gives a solution with a smaller memory requirement and more flexibility than using a wrapper.

回答2:

Thanks ravenspoint...!! I did what you said.. It works flawless! here is my AddData() function:

void mpFXYVector::AddData(float x, float y, std::vector<double> &xs, std::vector<double> &ys)
    {
        // Check if the data vectora are of the same size
        if (xs.size() != ys.size()) {
            wxLogError(_("wxMathPlot error: X and Y vector are not of the same length!"));
            return;
        }

        //Delete first point if you need a filo buffer (i dont need it)
        //xs.erase(xs.begin());
        //xy.erase(xy.begin());

        //Add new Data points at the end
        xs.push_back(x);
        ys.push_back(y);


        // Copy the data:
        m_xs = xs;
        m_ys = ys;

        // Update internal variables for the bounding box.
        if (xs.size()>0)
        {
            m_minX  = xs[0];
            m_maxX  = xs[0];
            m_minY  = ys[0];
            m_maxY  = ys[0];

            std::vector<double>::const_iterator  it;

            for (it=xs.begin();it!=xs.end();it++)
            {
                if (*it<m_minX) m_minX=*it;
                if (*it>m_maxX) m_maxX=*it;
            }
            for (it=ys.begin();it!=ys.end();it++)
            {
                if (*it<m_minY) m_minY=*it;
                if (*it>m_maxY) m_maxY=*it;
            }
            m_minX-=0.5f;
            m_minY-=0.5f;
            m_maxX+=0.5f;
            m_maxY+=0.5f;
        }
        else
        {
            m_minX  = -1;
            m_maxX  = 1;
            m_minY  = -1;
            m_maxY  = 1;
        }
    }

in the Main() you only have to:

m_Vector->AddData(xPos,yPos,vectorX, vectorY);
m_plot->Fit();

回答3:

I know this is an old thread but I needed to plot a scrolling X axis with wxMathPlot.

I've done a simple modification to jayjo's code to make X axis scrolling work.

I hoe this helps.

void mpFXYVector::AddData(float x, float y, std::vector<double> &xs, std::vector<double> &ys)
{
    // Check if the data vectora are of the same size
    if (xs.size() != ys.size()) {
        wxLogError(_("wxMathPlot error: X and Y vector are not of the same length!"));
        return;
    }

    //After a certain number of points implement a FIFO buffer
    //As plotting too many points can cause missing data
    if (x > 300)
    {
        xs.erase(xs.begin());
        ys.erase(ys.begin());
    }



    //Add new Data points at the end
    xs.push_back(x);
    ys.push_back(y);


    // Copy the data:
    m_xs = xs;
    m_ys = ys;

    // Update internal variables for the bounding box.
    if (xs.size()>0)
    {
        m_minX  = xs[0];
        m_maxX  = xs[0];
        m_minY  = ys[0];
        m_maxY  = ys[0];

        std::vector<double>::const_iterator  it;

        for (it=xs.begin();it!=xs.end();it++)
        {
            if (*it<m_minX) m_minX=*it;
            if (*it>m_maxX) m_maxX=*it;
        }
        for (it=ys.begin();it!=ys.end();it++)
        {
            if (*it<m_minY) m_minY=*it;
            if (*it>m_maxY) m_maxY=*it;
        }
        m_minX-=0.5f;
        m_minY-=0.5f;
        m_maxX+=0.5f;
        m_maxY+=0.5f;
    }
    else
    {
        m_minX  = -1;
        m_maxX  = 1;
        m_minY  = -1;
        m_maxY  = 1;
    }
}

回答4:

I do not have any personal experience with wxMathPlot, but I have been working with wxWidgets for years and highly recommend it for cross platform gui programming in c++, with that said according to the wxWiki graphics page the Numerix Graphics Library can be used for real time data so maybe that can help you out. Good luck.

回答5:

Maybe someone will have same problem and will need it... I needed very fast plotting for showing the data from oscilloscope. I was getting the data in packets. I made few changes that made a code a lot of faster. First thing is to change the if state in function SetData from if (xs.size()>0) to if (!xs.empty). Then you should firstly add all of your data packet to the vector

Vector1_X.push_back(x);
Vector1_Y.push_back(y);

And after that you should fit and set data.

Vector1 ->SetData(Vector1_X,Vector1_Y); // add vectors to main vector
MathPlot1-> Fit(); //fit plot to the data
Vector1_X.clear(); //if you want to clear plot after every packet 
Vector1_Y.clear(); //you should use it

Your code in main function will be longer but function will be faster because you add all data "at once".

回答6:

We ended up using ChartDirector instead. It has a lot of capability and is fast.