Inconsitancies between plot_robertson_chart and behaviourindex_pcpt_robertsonwride

[BergJul]

plot_robertson_chart uses the simple normalization Qt, which applies well to clay-like soils. For sand-like soils, inconsistencies can be observed between plot_robertson_chart and behaviourindex_pcpt_robertsonwride. This is due to soil behaviour type index (Ic) calculated using Qtn.

As suggested by Robertson (2019), it could be more coherent plotting normalized SBTn charts according to Qtn instead of Qt. plot_robertson_chart can evolve by giving a plotting option between Qt or Qtn.

[snakesonabrain]

Thanks for the comment. I will change the plotting but will also include in the docstrong that the correlation behaviourindex_pcpt_robertsonwride needs to be executed before plotting with Qtn.