not showing DotLine in a for loop setting Samples with Qvector

Hi,

when I use a ForLoop for initialing a QVector<double>, and have a setPen like this:

Code:

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curve.setPen(Qt::red, 4, Qt::DotLine)

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, the plot can not show the DotLine style. code is:

Code:

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QVector<double> t(20);
    //t<<1<<2<<3<<4<<5<<6<<7<<8<<9; //if I replace this line with under ForLoop the problem is solved.
    for(int i=0;i<10;i++)
    {
        t[i]=i;
    }
    curve.setSamples(t,t );
    curve.setPen(Qt::red, 4, Qt::DotLine);
    curve.attach(&plot);
 
    plot.show();

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I uploaded a picture of this. Thanks for any help
Attachment 11568

You have a vector of 20 points, where the upper 10 points stay at the default value ( 0, 0 ). So your curve goes up and down - guess with the effect, that the dots of the down path fills the gaps of the up path somehow.

Uwe

@Uwe thanks!!! I have asked a question here. My data is stored in an array like double data[1000][100]. What is your idea about using setRawSamples instaed of setSamples to plot two selected columns of the data together. for example:

Code:

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for(int i=0;i<1000;i++)
{
    for(int j=0;j<100;j++)
    {
        data[i][j]=(i+1)*(j+1);
    }
}
  _curve[0]->setRawSamples(data[0],data[1],1000);//your idea using this instead of setSamples???

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So many thanks for any help.

Use QVector, it's easier and because of its copy on write semantics you also don't have any copying.

Uwe

@Uwe thanks so much. do you mean it is better to use this: setSamples (const QVector< double > &xData, const QVector< double > &yData)?

then I need to have a QVector in 2 Dimensional (2D). could you help me to convert "double data[1000][100]" to a 2D QVector?
So so many thanks for your help Uwe!!!

Quote:

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Originally Posted by Uwe

You have a vector of 20 points, where the upper 10 points stay at the default value ( 0, 0 ). So your curve goes up and down - guess with the effect, that the dots of the down path fills the gaps of the up path somehow.
Uwe

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Uwe, can it be prevented to go down and make it only go up ?

Sure fix your code.

Uwe

Quote:

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Originally Posted by Uwe

Sure fix your code.

Uwe

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Uwe, by making (i<20) in ForLoop it is ok, but somewhere I need it's be till 10 (i<10). how "curve.setSamples(t,t )" can be set till 10 and not till 20?

I repeat above code again:

Code:

---

QVector<double> t(20); //I need this size to be always 20.
        for(int i=0;i<10;i++)//I need somewhere "i" goes to 10 not to 20
        {
            t[i]=i;
        }
        curve.setSamples(t,t );
        curve.setPen(Qt::red, 4, Qt::DotLine);
        curve.attach(&plot);
 
        plot.show();

---

one way is to resize t by t.resize(10). is there any other idea?

Uwe, thanks so much for your patient. my another question is:
Advantages of setRawSamples to setSamples is: in setRawSamples there is no copy and it uses the passing addresses of "x" and "y" but in setSamples there is a deep copy (even we can delete and free memory after deep copy). am I right?
thanks a lot for more help

Quote:

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Originally Posted by Alex22

Advantages of setRawSamples to setSamples is: in setRawSamples there is no copy and it uses the passing addresses of "x" and "y" but in setSamples there is a deep copy (even we can delete and free memory after deep copy). am I right?

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No QVector ( like all Qt containers ) is implicitly shared. But I'm not going to explain this any further - Qt documentation does it better than I could do.

Uwe

PS: this forum is related to Qwt, please use the Newbie section, when having Qt/C++ beginner questions