ggplot position dodge with position stack


Right now I have the error message

Warning in Ops.factor(var_1, as.numeric(barwidth)) :
  ‘+’ not meaningful for factors
Warning: Removed 14 rows containing missing values (position_stack).

It's very difficult to use ggplot2 ( certainly I'm not expert with R code...)

Other point, I try to use the example code and it's not ok , the message is

Error in UseMethod("filter_") : 
  no applicable method for 'filter_' applied to an object of class "function"