Programmatically creating Markdown tables in R with KnitR

Question

I am just starting to learn about KnitR and the use of Markdown in generating R documents and reports. This looks to be perfect for a lot of the day to day reporting that I

Answer 1

To write / create Markdown tables in R, you can also use MarkdownReports' MarkDown_Table_writer_DF_RowColNames() or MarkDown_Table_writer_NamedVector() functions. You just pass on a data frame / matrix with dimension names, or a vector with names, and it parses & writes out the table in Markdown format.

Answer 2

My function for Gitlab:

to_markdown<-function(df) {
    wrap<-function(x,sep=" ") paste0("|", sep, paste(x, collapse=paste0(sep,"|",sep)), sep, "|", sep=sep)
    paste0(wrap(colnames(df)),
    "\n",
    wrap(rep("------", ncol(df)),sep=""),
    "\n",
    paste(apply(df, 1, wrap), collapse="\n"))
}

cat(to_markdown(head(iris[,1:3])))

| Sepal.Length | Sepal.Width | Petal.Length | 
|------|------|------|
| 5.1 | 3.5 | 1.4 | 
| 4.9 | 3 | 1.4 | 
| 4.7 | 3.2 | 1.3 | 
| 4.6 | 3.1 | 1.5 | 
| 5 | 3.6 | 1.4 | 
| 5.4 | 3.9 | 1.7 | 

Answer 3

use a combination of knitr::kable and xtable in your markdown document.

library("knitr","xtable")

for a simple data.frame -

kable(head(mtcars[,1:4]),format="markdown")
kable(head(mtcars[,1:4]),format="pandoc",caption="Title of the table")

format="pandoc" allows more options like caption.

Now the combination for model summary.

data(tli)
fm1 <- aov(tlimth ~ sex + ethnicty + grade + disadvg, data=tli)
kable(xtable(fm1), caption = "Annova table")

for even more options look at stargazer package instead of xtable.

example for personal use

Answer 4

Now knitr (since version 1.3) package include the kable function for a creation tables:

> library(knitr)
> kable(head(iris[,1:3]), format = "markdown")
|  Sepal.Length|  Sepal.Width|  Petal.Length|
|-------------:|------------:|-------------:|
|           5,1|          3,5|           1,4|
|           4,9|          3,0|           1,4|
|           4,7|          3,2|           1,3|
|           4,6|          3,1|           1,5|
|           5,0|          3,6|           1,4|
|           5,4|          3,9|           1,7|

UPDATED: if you get raw markdown in a document try setup results = "asis" chunk option.

Answer 5

There are functions in the pander package:

> library(pander)
> pandoc.table(head(iris)[, 1:3])

-------------------------------------------
 Sepal.Length   Sepal.Width   Petal.Length 
-------------- ------------- --------------
     5.1            3.5           1.4      

     4.9             3            1.4      

     4.7            3.2           1.3      

     4.6            3.1           1.5      

      5             3.6           1.4      

     5.4            3.9           1.7      
-------------------------------------------

Answer 6

Two packages that will do this are pander

library(devtools)
install_github('pander', 'Rapporter')

Or ascii

pander is a slightly different approach to report construction, (but can be useful for this feature).

ascii will allow you to print with type = 'pandoc (or various other markdown flavours)

library(ascii)
print(ascii(head(iris[,1:3])), type = 'pandoc')



    **Sepal.Length**   **Sepal.Width**   **Petal.Length**  
--- ------------------ ----------------- ------------------
1   5.10               3.50              1.40              
2   4.90               3.00              1.40              
3   4.70               3.20              1.30              
4   4.60               3.10              1.50              
5   5.00               3.60              1.40              
6   5.40               3.90              1.70              
--- ------------------ ----------------- ------------------

Note that in both these cases, it is directed towards using pandoc to convert from markdown to your desired document type, however using style='rmarkdown' will create tables that are compatible with this markdown package and inbuilt conversion in rstudio.