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