Use filtered data in 'server context' in text - shiny

[caiolivf]

Description

Initially, I am filtering my data according to user input. Next, I would like to insert dynamic objects into the body of the text, such as: inserting an average of the filtered data in the text.

---
title: "Iris K-Means Clustering"
format: 
  html:
    page-layout: custom
server: shiny
---

```{r}
#| panel: sidebar
vars <- setdiff(names(iris), "Species")
selectInput('xcol', 'X Variable', vars)
selectInput('ycol', 'Y Variable', vars, selected = vars[[2]])
numericInput('clusters', 'Cluster count', 3, min = 1, max = 9)
```

```{r}
#| panel: fill
plotOutput('plot1')
```

```{r}
#| context: server
selectedData <- reactive({
    iris[, c(input$xcol, input$ycol)]
  })

clusters <- reactive({
  kmeans(selectedData(), input$clusters)
})

output$plot1 <- renderPlot({
  palette(c("#E41A1C", "#377EB8", "#4DAF4A", "#984EA3",
    "#FF7F00", "#FFFF33", "#A65628", "#F781BF", "#999999"))

  par(mar = c(5.1, 4.1, 0, 1))
  plot(selectedData(),
       col = clusters()$cluster,
       pch = 20, cex = 3)
  points(clusters()$centers, pch = 4, cex = 4, lwd = 4)
})
```

The sepal width mean is `r mean(selectedData()[, 2])`

Additionally, I would like to know if it is possible to create multiple chunks with #|context: server - my document has texts between plots and tables (which must be within a #|context: server).

[cderv]

Next, I would like to insert dynamic objects into the body of the text, such as: inserting an average of the filtered data in the text.

If you want to use a value from a shiny context, you need to build the UI in the shiny context too, using the value.

So you need to build you UI element using shiny in that case I believe

---
title: "Iris K-Means Clustering"
format: 
  html:
    page-layout: custom
server: shiny
---

```{r}
#| panel: sidebar
vars <- setdiff(names(iris), "Species")
selectInput('xcol', 'X Variable', vars)
selectInput('ycol', 'Y Variable', vars, selected = vars[[2]])
numericInput('clusters', 'Cluster count', 3, min = 1, max = 9)
```

```{r}
#| panel: fill
plotOutput('plot1')
```

```{r}
#| context: server
selectedData <- reactive({
    iris[, c(input$xcol, input$ycol)]
  })

clusters <- reactive({
  kmeans(selectedData(), input$clusters)
})

output$plot1 <- renderPlot({
  palette(c("#E41A1C", "#377EB8", "#4DAF4A", "#984EA3",
    "#FF7F00", "#FFFF33", "#A65628", "#F781BF", "#999999"))

  par(mar = c(5.1, 4.1, 0, 1))
  plot(selectedData(),
       col = clusters()$cluster,
       pch = 20, cex = 3)
  points(clusters()$centers, pch = 4, cex = 4, lwd = 4)
})
```

```{r}
shiny::htmlOutput("synthesis")
```

```{r}
#| context: server
output$synthesis <- renderUI({
  markdown(glue::glue("The **sepal width mean** is { mean(selectedData()[, 2]) }"))
})
```

Additionally, I would like to know if it is possible to create multiple chunks with #|context: server - my document has texts between plots and tables (which must be within a #|context: server).

Yes you can have several context

Overall this is not a Quarto specific question and you could find more about shiny and rmarkdown usage on the web (as rmarkdown is older). It would work the same.

Also asking on shiny forum could help too (like https://community.rstudio.com/c/shiny/8)

Hope it helps