TODO

- Data consistency checking continuity of dates and non-existent values in some days (e.g, feb 30th);
- Define y limit based on all input data for all graphs;
- Define functions for estimating values for missing data;
- Provide another distribution possibilities for SPI analysis;  
- Implement weekly scale for PN analysis;
- Change "for" loops by lapply for input lists in order to increase performance;
- Simplifying the function's names
- Undocumented code objects:
  ‘as.decade’ 
  ‘as.deciles’ 
  ‘as.fd’ 
  ‘as.precintcon.decade’
  ‘as.precintcon.deciles’ 
  ‘as.precintcon.fd’ 
  ‘precintcon.A’
  ‘precintcon.H’ 
  ‘precintcon.S’ 
  ‘precintcon.Z’ 
  ‘precintcon.alpha’
  ‘precintcon.b’ 
  ‘precintcon.beta’ 
  ‘precintcon.ci’
  ‘precintcon.classification’ 
  ‘precintcon.fd’ 
  ‘precintcon.gamma’
  ‘precintcon.ln.a’ 
  ‘precintcon.max’ 
  ‘precintcon.min’
  ‘precintcon.monthly.aggregation’ 
  ‘precintcon.pn’ 
  ‘precintcon.r.squared’
  ‘precintcon.trend.test’