====== URLs ======

  * https://towardsdatascience.com/a-guide-to-data-visualisation-in-r-for-beginners-ef6d41a34174
  * http://paldhous.github.io/ucb/2016/dataviz/week2.html   !!!!!
  * http://paldhous.github.io/ucb/2016/dataviz/
  * Stanford Encyclopedia of Philosophy https://plato.stanford.edu/ ; http://dailynous.com/2018/12/20/structure-stanford-encylopedia-philosophy-time-visualized/
  * https://github.com/hadley/vis-eda/blob/master/vis-eda.pdf
  * https://usdawatercolors.nal.usda.gov/pom/home.xhtml
  * Prikaz skupin: https://cran.r-project.org/web/packages/ClusVis/index.html ; https://cran.r-project.org/web/packages/ClusVis/ClusVis.pdf
  *