Change the name of the plot to avoid overwriting

When issuing the report, it outputs a png file called plot_deviations. If you run the report script again (with difference data set, such as a different sensor), the plot_deviations.png will be overwritten. A possible solution could be to include the name of the report in the name of the plot deviations - which would become, for example, something like Report1-plot_deviations.png.