Error(s) in re-building vignettes:
  ...
--- re-building ‘estudy2-intro.Rmd’ using rmarkdown
'getSymbols' currently uses auto.assign=TRUE by default, but will
use auto.assign=FALSE in 0.5-0. You will still be able to use
'loadSymbols' to automatically load data. getOption("getSymbols.env")
and getOption("getSymbols.auto.assign") will still be checked for
alternate defaults.

This message is shown once per session and may be disabled by setting 
options("getSymbols.warning4.0"=FALSE). See ?getSymbols for details.

Warning: ALV.DE contains missing values. Some functions will not work if objects contain missing values in the middle of the series. Consider using na.omit(), na.approx(), na.fill(), etc to remove or replace them.
Warning: CS.PA contains missing values. Some functions will not work if objects contain missing values in the middle of the series. Consider using na.omit(), na.approx(), na.fill(), etc to remove or replace them.
Warning: G.MI contains missing values. Some functions will not work if objects contain missing values in the middle of the series. Consider using na.omit(), na.approx(), na.fill(), etc to remove or replace them.
Warning: HNR1.HA contains missing values. Some functions will not work if objects contain missing values in the middle of the series. Consider using na.omit(), na.approx(), na.fill(), etc to remove or replace them.
Warning: HSX.L contains missing values. Some functions will not work if objects contain missing values in the middle of the series. Consider using na.omit(), na.approx(), na.fill(), etc to remove or replace them.
Warning: MUV2.DE contains missing values. Some functions will not work if objects contain missing values in the middle of the series. Consider using na.omit(), na.approx(), na.fill(), etc to remove or replace them.
Warning: TOP.CO contains missing values. Some functions will not work if objects contain missing values in the middle of the series. Consider using na.omit(), na.approx(), na.fill(), etc to remove or replace them.
Warning: ^STOXX50E download failed; trying again.
Quitting from lines 69-74 (estudy2-intro.Rmd) 
Error: processing vignette 'estudy2-intro.Rmd' failed with diagnostics:
Unable to import "^STOXX50E".
^STOXX50E download failed after two attempts. Error message:
HTTP error 400.
--- failed re-building ‘estudy2-intro.Rmd’

SUMMARY: processing the following file failed:
  ‘estudy2-intro.Rmd’

Error: Vignette re-building failed.
Execution halted