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Thread: not showing DotLine in a for loop setting Samples with Qvector

  1. #1
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    Default 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:
    Qt Code:
    1. curve.setPen(Qt::red, 4, Qt::DotLine)
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    , the plot can not show the DotLine style. code is:


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

    I uploaded a picture of this. Thanks for any help
    NotShowStyle.png

  2. #2
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    Default Re: not showing DotLine in a for loop setting Samples with Qvector

    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

  3. The following user says thank you to Uwe for this useful post:

    Alex22 (10th December 2015)

  4. #3
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    Default Re: not showing DotLine in a for loop setting Samples with Qvector

    @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:
    Qt Code:
    1. for(int i=0;i<1000;i++)
    2. {
    3. for(int j=0;j<100;j++)
    4. {
    5. data[i][j]=(i+1)*(j+1);
    6. }
    7. }
    8. _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.
    Last edited by Alex22; 10th December 2015 at 12:25.

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    Default Re: not showing DotLine in a for loop setting Samples with Qvector

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

    Uwe

  6. The following user says thank you to Uwe for this useful post:

    Alex22 (10th December 2015)

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    Default Re: not showing DotLine in a for loop setting Samples with Qvector

    @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!!!

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    Default Re: not showing DotLine in a for loop setting Samples with Qvector

    Quote Originally Posted by Uwe View Post
    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, can it be prevented to go down and make it only go up ?

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    Default Re: not showing DotLine in a for loop setting Samples with Qvector

    Sure fix your code.

    Uwe

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    Default Re: not showing DotLine in a for loop setting Samples with Qvector

    Quote Originally Posted by Uwe View Post
    Sure fix your code.

    Uwe
    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:

    Qt Code:
    1. QVector<double> t(20); //I need this size to be always 20.
    2. for(int i=0;i<10;i++)//I need somewhere "i" goes to 10 not to 20
    3. {
    4. t[i]=i;
    5. }
    6. curve.setSamples(t,t );
    7. curve.setPen(Qt::red, 4, Qt::DotLine);
    8. curve.attach(&plot);
    9.  
    10. plot.show();
    To copy to clipboard, switch view to plain text mode 

    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

  11. #9
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    Default Re: not showing DotLine in a for loop setting Samples with Qvector

    Quote Originally Posted by Alex22 View Post
    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?
    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

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