User Input to QtexEdit to extract Matrix elements

[Warrior4just]

Thanks a lot Raven-woks...that was helpful

what does the bool do inside the .todouble() method, interesting...i suppose i understand it, but i didn't think .todouble() method could take a reference bool argument.

My issue now, is the fact that i don' t know how to retrieve the data from the 2D Qlist to display them to QtextEdit.

i just would like to know how to print a 2D Qlist to QtextEdit which takes only strings

Thanks a lot for your help

[raven-worx]

[quote author="Warrior4just" date="1390409926"]
what does the bool do inside the .todouble() method, interesting...i suppose i understand it, but i didn't think .todouble() method could take a reference bool argument.
[/quote]
In case the string can not be converted to a numeric value the bool is set to false.
The QString::toDouble() doesn't take a reference bool variable, but an optional pointer variable.

[quote author="Warrior4just" date="1390409926"]
My issue now, is the fact that i don' t know how to retrieve the data from the 2D Qlist to display them to QtextEdit.

i just would like to know how to print a 2D Qlist to QtextEdit which takes only strings
[/quote]
Build your string using QString::number() with the values from the list. Also insert "\n" wherever you need it.

[daemon777]

For building longer Strings the arg-Method from QString can be quite usefull.
Something like QString output = QString("%1 \n%2").arg("String 1",someint) is a very fast way to build such a string.

[Warrior4just]

Thank you Raven-workx and Deamon777
Great...
But if i wanna use QString::number() , i need to build two loops for each index of the list
How does one select the indices of 2D List matrix (e.g. rows and colums), i know im' probably thinking in terms of scientific programming, but u seem where i'm going , i(m using the Eigen librabry afterwards
say
@
for (int i , i < matrix.row(), i++)
{
for (int j , j< matrix.cols(),j++)
QString qsval= matrix[j][i].QString::number();
ui->textEdit_7->setPlainText(qsval);
}
}
@

Thank you for clarifying...

[raven-worx]

Beside you are missing some error checks:
@
QString text;
for (int i , i < matrix.row(), i++)
{
for (int j , j< matrix.cols(),j++)
{
text += QString::number(matrix[j][i]);
}
text += "\n";
}
ui->textEdit_7->setPlainText(text);
@

[Warrior4just]

Raven-workx

i don't think what i wrote is correct (assuming i fixed the syntax errors), because, matrix is a QList<Qlist<double>> ...so writing matrix.rows() makes no sense..
How do i access the length of matrix : numbers of rows
How do i access the width of matrix: number of columns

Thank you

[SGaist]

Hi,

"QList::count()":http://qt-project.org/doc/qt-5/qlist.html#count-2 to get the number of item

[Warrior4just]

SGalst

but @Qlist@ is 2D list....

count would be for rows or cols...and what's for the other

thanks bro

[raven-worx]

yes calling count() on the outermost list is for rows. Calling count() on the QList of an row returns the column count. of this row.
Actually it's very similar to a multi-dimensional array.

You could also avoid the indices at all:
@
QString text;
foreach( QList<double> row, matrix ) //rows
{
foreach( double colValue, row ) //cols
{
text += QString::number(colValue);
}
text += "\n";
}
ui->textEdit_7->setPlainText(text);
@

[Warrior4just]

Thanks a lot raven-worx for your help, worked well

there is one little problem , is that i am unable to display Matrix elements of Eigen's Matrix class of the Eigen library for linear algebra , here is what i did when i wanted to solve an example of a linear system.

i can't show the numbers in text edits (text edit 5 and 6)

@void MainWindow::on_pushButton_5_clicked()
{
MatrixXd A = MatrixXd::Random(3,3);
VectorXd b = VectorXd::Random(3,1);

QString text1;
QString text2;

for (int i; i<=A.rows();i++)
{
    for (int j;j<=A.cols();j++)
    {
        text1 += QString::number(A(i,j))+ " ";

    }

    text1 += "\n";
    text2 +=  QString::number(b(i))+ "\n";
}

 ui->textEdit_5->setPlainText(text1);
 ui->textEdit_6->setPlainText(text2);

 //    Vector3f x = A.colPivHouseholderQr().solve(b);

}@

I appreciate it