### Cumulated histogram

We can represent the cumulated histogram. It is a function which computes, for each value, the proportion of individuals below this value. 
It can be written as 
    
   $$F(z_c) =\frac{1}{n}\sum_{i=1}^n 1\!\!\!1_{]z_{i},+\infty]}(z_c)$$
   
   where $1\!\!\!1_A$ is the indicator function of the set $A$:
   
   $$1\!\!\!1_A(x)=\left\{\begin{array}{ccc}1 &\textrm{ if } & x\in A\\
   0 & \textrm{ otherwise } & \end{array}
   \right.$$