For the K Desktop Environment (KDE, https://www.kde.org/), I have in particular developed the program Kpl.
Kpl is used for two- and three-dimensional graphical visualization of data sets and functions. In addition, nonlinear fits of function parameters to data sets can be performed. Also general linear regression and smoothing spline interpolation are possible.
Homepage of Kpl
SEIR model calculator
With the SEIR model calculator calculations on epidemics as the COVID-19 pandemic can be performed on base of the SEIR model (https://en.wikipedia.org /wiki/Compartmental_models_in_ epidemiology#The_SEIR_model).
Dew point calculator
The dew point temperature (https://en.wikipedia.org/wiki/Dew_point) of humid air is the temperature at which the water starts to condense when it cools down. Using the dew point calculator you can calculate the dew point temperature from the air temperature and the relative air humidity.
Relative air humidity φ in dependence of the air temperature ϑ for different constant values of the dew point temperature τ. Air is experienced as muggy when the dew point temperature exceeds 16 °C. This is the case when the relative air humidiy at the actual air temperature is above the black curve for τ = 16 °C.
Sunrise and sunset
With this calculator the times of sunrise and sunset can be calculated for locations with given geographical coordinates. If geolocation is supported (particularly using GPS) by the device, the actual position can be determined for this.
Times (Central European Summer Time CEST: MESZ) of sunrise and sunset for Freiburg im Breisgau, Germany, in the year 2020.
With the UTM converter geographic coordinates can be converted from longitude and latitude to UTM coordinates (https://en.wikipedia.org/wiki/Universal_Transverse_Mercator_coordinate_system) and vice versa. If geolocation is supported (particularly using GPS) by the device, the actual position can be determined for this.