This script serves as Supplementary Information for the manuscript "Narrow, fast, and “cold” mantle plumes caused by strain-weakening rheology in Earth’s lower mantle" by Gülcher et al., G-cubed, 2022. It relates to Supplementary Information Text S1 and Figures S1 and S2. The script is use to visualise the evolution of a strain ellipse during different types of deformation, and during 'rheological healing' as implemented in the numerical study. The data shown in Figures S1 and S2 can herewith be reproduced. The set of parameters used for each plot are defined at the header of the MATLAB script. For details regarding this script and the results it reproduces, the reader is referred to the manuscript.