scaling of widgets in verticalLayout

[Surfman19]

Hello,

i have a QMainWindow with a QVBoxLayout and added QwtPlot and QPlainTextEdit.

at the moment both the QwtPlot and QPlainTextEdit have the same size...

how can i make QwtPlot larger than the QwtPlot?

i tried to play with the stretch factor... but this did not change the layout of the widgets... any idea what im doing wrong?

ui->verticalLayout->setStretchFactor(ui->plainTextEdit, 1);
ui->verticalLayout->setStretchFactor(plot, 2);

ui->verticalLayout->setStretchFactor(ui->plainTextEdit, 1);
ui->verticalLayout->setStretchFactor(plot, 2);

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Thanks,
A