organize reactivity with pre-loaded data - r

Question

I have couple of tables stored each in a separate txt file, and also combined in a single Rdat file, something like this:
# generate tables
df.A <- data.frame(colA1=letters[1:20],colA2=LETTERS[1:20], stringsAsFactors = F)
df.B <- data.frame(colB1=rnorm(20),colB2=rnorm(20), stringsAsFactors = F)
# save tables as separate files
write.csv(df.A, 'tableA.txt')
write.csv(df.B, 'tableB.txt')
# I may have more tables
# save all tables in a single Rdat file
save(df.A,df.B, file = 'alldata.RDat')
Now in my shiny markdown document, I want to pre-load those tables from the RDat file, but also give user a possibility to re-load them a) separately from individual files, or b) altogether from the RDat file. Here is the first version I came to:
---
runtime: shiny
output: html_document
---
```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = FALSE)
```
```{r}
load('alldata.RDat')
```
Tables below:
```{r}
inputPanel(
actionButton('load.A','Reload Table A'),
actionButton('load.B','Reload Table B'),
actionButton('load.Rdat','Load all from Rdat file')
)
tabsetPanel(type = "tabs",
tabPanel("table A", dataTableOutput("toA")),
tabPanel("table B", dataTableOutput("toB"))
)
# next 2 lines render pre-loaded tables before any buttons are pressed:
output$toA <- renderDataTable(df.A, options=list(pageLength=5))
output$toB <- renderDataTable(df.B, options=list(pageLength=5))
observeEvent(input$load.A, {
df.A <- read.csv('tableA.txt');
output$toA <- renderDataTable(df.A, options=list(pageLength=5))
})
observeEvent(input$load.B, {
df.B <- read.csv('tableB.txt');
output$toB <- renderDataTable(df.B, options=list(pageLength=5))
})
observeEvent(input$load.Rdat, {
load('alldata.RDat', verbose = T);
output$toA <- renderDataTable(df.A, options=list(pageLength=5));
output$toB <- renderDataTable(df.B, options=list(pageLength=5))
})
```
It works fine, but I have a feeling it is not the proper way to use reactivity. For example, every time after updating my table object (df.A or dfB), I have to call render explicitly output$toA <- renderDataTable(...) (3 times for each table!).
One solution I had in mind was to put my tables into reactiveValues(), which gave the following:
---
runtime: shiny
output: html_document
---
```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = FALSE)
```
```{r}
load('alldata.RDat')
```
Tables below:
```{r}
inputPanel(
actionButton('load.A','Reload Table A'),
actionButton('load.B','Reload Table B'),
actionButton('load.Rdat','Load all from Rdat file')
)
tabsetPanel(type = "tabs",
tabPanel("table A", dataTableOutput("toA")),
tabPanel("table B", dataTableOutput("toB"))
)
rv <- reactiveValues(df.A = df.A, df.B = df.B)
output$toA <- renderDataTable(rv$df.A, options=list(pageLength=5))
output$toB <- renderDataTable(rv$df.B, options=list(pageLength=5))
observeEvent(input$load.A, {
rv$df.A <- read.csv('tableA.txt');
})
observeEvent(input$load.B, {
rv$df.B <- read.csv('tableB.txt');
})
observeEvent(input$load.Rdat, {
load('alldata.RDat', verbose = T);
rv$df.A <- df.A;
rv$df.B <- df.B;
})
```
This looks better because I have only one call of each renderDataTable() in my code. But now each of my tables are stored in memory twice - one in df.A (as loaded from 'alldata.RDat') and another one in rv$df.A... Does it make sense at all, or there's a more kosher way to solve these kinds of things?

Answer 1

You would like to load the data for df.A and df.B from either a csv or Rdat file. This almost certainly requires an intermediate variable, rv as you have correctly created.
The second example you have created is much better than the first, we must avoid multiple render calls to the same output, especially render calls inside an observer.
The code below executes load('alldata.RDat', verbose = T) from within the observer and the initial values of rv are set from within the observer instead of using the global load('alldata.RDat', verbose = T). This prevents the data from being loaded twice.
---
runtime: shiny
output: html_document
---
```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = FALSE)
```
```{r}
#load('alldata.RDat')
```
Tables below:
```{r}
inputPanel(
actionButton('load.A','Reload Table A'),
actionButton('load.B','Reload Table B'),
actionButton('load.Rdat','Load all from Rdat file')
)
tabsetPanel(type = "tabs",
tabPanel("table A", dataTableOutput("toA")),
tabPanel("table B", dataTableOutput("toB"))
)
rv <- reactiveValues(df.A = NULL, df.B = NULL)
output$toA <- renderDataTable({
req(rv$df.A)
rv$df.A
}, options=list(pageLength=5))
output$toB <- renderDataTable({
req(rv$df.B)
rv$df.B
}, options=list(pageLength=5))
observeEvent(input$load.A, {
rv$df.A <- read.csv('tableA.txt');
})
observeEvent(input$load.B, {
rv$df.B <- read.csv('tableB.txt');
})
observeEvent(c(input$load.Rdat), {
load('alldata.RDat', verbose = T);
rv$df.A <- df.A;
rv$df.B <- df.B;
})
```