fix link to next chapter

session_1/session_1.Rmd

@@ -1084,4 +1084,4 @@ sessionInfo()
 browseVignettes("ggplot2")
 ```
 
-### See you in [Session 2 : "Introduction to Tidyverse"](https://can.gitbiopages.ens-lyon.fr/R_basis/session_2.html)
+### See you in [R.2: "Introduction to Tidyverse"](/session_2/session_2.html)

session_2/session_2.Rmd

@@ -562,7 +562,7 @@ ggplot(data = new_mpg, mapping = aes(x = displ, y = hwy, color = fuel)) +
 </p>
 </details>
 
-### See you in [R.3: Transformations with ggplot2](https://can.gitbiopages.ens-lyon.fr/R_basis/session_3.html)
+### See you in [R.3: Transformations with ggplot2](/session_3/session_3.html)
 
 ## To go further: publication ready plots
 

session_3/session_3.Rmd

@@ -333,7 +333,7 @@ ggplot(data = diamonds, mapping = aes(x = cut, fill = cut)) +
 
 By combining the right **geom**, **coordinates** and **faceting** functions, you can build a large number of different plots to present your results.
 
-## See you in [R.4: data transformation](https://can.gitbiopages.ens-lyon.fr/R_basis/session_4.html)
+## See you in [R.4: data transformation](/session_4/session_4.html)
 
 ## To go further:  animated plots from xls files
 

session_5/session_5.Rmd

@@ -388,4 +388,4 @@ flights %>%
 </p>
 </details>
 
-### See you in [R.6: tidydata](https://can.gitbiopages.ens-lyon.fr/R_basis/session_6/)
+### See you in [R.6: tidydata](/session_6/session_6.html)

session_6/session_6.Rmd

@@ -318,4 +318,4 @@ These expect the x and y inputs to have the same variables, and treat the observ
 knitr::include_graphics('img/overview_set.png')
 ```
 
-### See you in [R.7: String & RegExp](https://can.gitbiopages.ens-lyon.fr/R_basis/session_7/)
+### See you in [R.7: String & RegExp](/session_7/session_7.html)

session_7/session_7.Rmd

@@ -429,4 +429,4 @@ sentences %>%
   str_split("\\s")
 ```
 
-### See you in [R.8: Factors](https://can.gitbiopages.ens-lyon.fr/R_basis/session_8/)
\ No newline at end of file
+### See you in [R.8: Factors](/session_8/session_8.html)
\ No newline at end of file