Fix remaining r ... expressions

Author: aitap

vignettes/datatable-intro.Rmd

@@ -635,7 +635,11 @@ DT[, print(c(a,b)), by = ID] # (1)
 DT[, print(list(c(a,b))), by = ID] # (2)
 ```
 
-In (1), for each group, a vector is returned, with length = 6,4,2 here. However, (2) returns a list of length 1 for each group, with its first element holding vectors of length 6,4,2. Therefore, (1) results in a length of ` 6+4+2 = `r 6+4+2``, whereas (2) returns `1+1+1=`r 1+1+1``.
+```{r, echo = FALSE}
+p = function(x) paste0('<code>', paste(deparse(substitute(x)), collapse = ' '), ' = ', x, '</code>')
+```
+
+In (1), for each group, a vector is returned, with length = 6,4,2 here. However, (2) returns a list of length 1 for each group, with its first element holding vectors of length 6,4,2. Therefore, (1) results in a length of `{r} p(6+4+2)`, whereas (2) returns `{r} p(1+1+1)`.
 
 Flexibility of j allows us to store any list object as an element of data.table.  For example, when statistical models are fit to groups, these models can be stored in a data.table.  Code is concise and easy to understand.
 

vignettes/datatable-keys-fast-subset.Rmd

@@ -441,7 +441,7 @@ dim(ans2)
 identical(ans1$val, ans2$val)
 ```
 
-* The speed-up is **~`r round(t1[3]/max(t2[3], .001))`x**!
+* The speed-up is **~`{r} round(t1[3]/max(t2[3], .001))`x**!
 
 ### b) Why does keying a *data.table* result in blazing fast subsets?