Register the plantuml knitr engine

The plantuml knitr engine plantuml_knit_engine() needs to be registered with knitr. This is done automatically when loading the package plantuml.

library(plantuml)

PlantUML Code Chunk Options

The following options are available, in addition to the standard options:

plantuml_format: the format of the resulting file. At the moment, png (the default), svg, and eps are implemented.
plantuml.path: the path at which the resulting graphs should be saved. If the directory does not exist, it will be created.
plantuml.preview: if the graph should be shown as an inline preview in the Rmarkdown document in Rstudio. This option results in generating the image twice, which may lead to a substantial increase of the processing time. The preview is always a vector preview, irrespective of the file plantuml_format

A simple chart as png

A png grph is nice, because it can be shown in all kinds of documents, including html, pdf and docx. But it is a bitmap format, i.e. when scaling in the grapoh becomes pixelated.

A simple chart as png and with code

To also show the plantuml code, you have to set echo = TRUE:

left to right direction
actor "Food Critic" as fc
package Restaurant {
  usecase "Eat Food" as UC1
  usecase "Pay for Food" as UC2
  usecase "Drink" as UC3
}
fc --> UC1
fc --> UC2
fc --> UC3

A simple chart using format `auto` with code

When specifying plantuml.format = "auto" the apropriate vector format is chosen for the output format:

pdf output format: pdf as plantuml.format
html output format: svg as plantuml.format
docx output format: pdf as plantuml.format

Therefore, the vector format appropritw for the output format is is chosen for the output format.

robust "DNS Resolver" as DNS
robust "Web Browser" as WB
concise "Web User" as WU

@0
WU is Idle
WB is Idle
DNS is Idle

@+100
WU -> WB : URL
WU is Waiting
WB is Processing

@+200
WB is Waiting
WB -> DNS@+50 : Resolve URL

@+100
DNS is Processing

@+300
DNS is Idle

Now only the code

@startuml
Alice -> Bob: Authentication Request
Bob --> Alice: Authentication Response

Alice -> Bob: Another authentication Request
Alice <-- Bob: Another authentication Response
@enduml

And now as ASCII Art

This does not play nicely with LaTeX and therefore pdf due to unicode characters used. I have no idea at the moment how to make this nicer.

@startuml
Alice -> Bob: Authentication Request
Bob --> Alice: Authentication Response

Alice -> Bob: Another authentication Request
Alice <-- Bob: Another authentication Response
@enduml
     ┌─────┐                           ┌───┐
     │Alice│                           │Bob│
     └──┬──┘                           └─┬─┘
        │    Authentication Request      │  
        │───────────────────────────────>│  
        │                                │  
        │    Authentication Response     │  
        │<─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─│  
        │                                │  
        │Another authentication Request  │  
        │───────────────────────────────>│  
        │                                │  
        │Another authentication Response │  
        │<─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─│  
     ┌──┴──┐                           ┌─┴─┐
     │Alice│                           │Bob│
     └─────┘                           └───┘

- Register the plantuml knitr engine

Use of plantuml with knitr