Install libqwt5-doc by entering the following commands in the terminal:
sudo apt update sudo apt install libqwt5-doc
Qt widgets library for technical applications (documentation)
The Qwt library contains Qt GUI Components and utility classes which are primarily useful for programs with a technical background. Most of these widgets are used to control or display values, arrays, or ranges of type double. . This package contains the Qwt library documentation and programming examples for developers. The documentation is generated for Qt4.