第 3 章 Process of Data Visualization

3.1 Drake: Program planning

Drake package:

3.1.1 Command block

For each command block, it behaves like a function body.

  • It can pass a value in the LAST line that produces a print oput.
  • Either global environment objects or target values can be used from outside the command block. Therefore, objects in other blocks can not be accessed unless it is passed to a target.

3.1.2 Build a plan

a <- 3
cc <- 15
examplePlan <- drake::drake_plan(
  target1 = {
    a + 5 -> b
    cc <- 0
    if (b < 10) b 
  },
  target2 = {
    cc 
  },
  target3 = {
    target1 + a
  }
)

Each target can only access other target values or object values in the global environment.

3.1.3 Make it happen

make(examplePlan)

3.1.4 Access target ex post

readd(target1)
readd(target2)
readd(target3)

or

loadd(target1)
loadd(target2)
loadd(target3)

If your work in a R project directory, once a drake plan is make()-ed, you can access target value via readd()/loadd() even if you restart your R session.

  • All targets are cached unless clean() is called.

3.1.5 Target dependency

vis_drake_graph(examplePlan)

3.1.6 Source and Output

planExample <-
  drake::drake_plan(
    target1 = {
      download.file("https://.....")
    },
    :
    :
    targetN = {
      save(someObject, "myResult.rda")
    }
  )

file_in/file_out

planExample <-
  drake::drake_plan(
    target1 = {
      download.file(file_in("https://....."))
    },
    :
    :
    targetN = {
      save(someObject, file_out("myResult.rda"))
    }
  )

  • file_in: once "https://....." content change, it will trigger remaking target1.

  • file_out: once "myResult.rda" is deleted, it will trigger remaking targetN.

file_in/file_out only support exogenous path specification, i.e. one "..." completes the path specificatioin. Paths generated by some operations like paste0(myroot,"data.txt") are not supported.

3.2 Cache

3.2.1 SOAR package

library(SOAR)
Attach() # attach .R_Cache 

obj1 <- 5
Store(obj1)

obj1 <- 3 # Won't change obj1 in cache, but create an obj1 in global environment.
Store(obj1) # Unless store it in cache.

Remove(obj1)

3.2.2 econDV::%=%

  • object %=% value: create object with value at the first time, and Store(object). When run object %=% value the second time, this command will be ignore.
library(WDI)
import_search <-
  WDIsearch(string = "Imports of goods and services")
world_import <-
    WDI(indicator = import_search[12, 1])
system.time(
  world_import <-
    WDI(indicator = import_search[12, 1])
)
library(econDV)
system.time(
  world_import %=%
    WDI(indicator = import_search[12, 1])
)
  • If world_import exists, it will be stored in R.Cache environment.

3.3 rmd2drake: Equip R Markdown with Drake

  • convert Rmd to a drake plan R script, which includes corresponding make/visualization function

  • can apply to multiple plans; each has its own cache.

範例檔案：taiwanXMGDPRatio.Rmd

3.3.1 Addins

Boxy SVG

probably only work in Mac OS

rmd2drake::svgOpen("....svg")