Method 2: observeEvent() and updateSelectInput – example code
This second variation of Method 2 uses observeEvent() with updateSelectInput(). With this method, you can specify which input control to observe – the first argument of observeEvent() is the ID of the control to observe.
---
title: "Shiny selectInput based on another selectInput"
runtime: shiny
output: html_document
---
```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = FALSE, error=TRUE)
```
```{r create_table_of_choices, eval=TRUE}
# table of choices for the selectInput controls
# note there's a duplicate item 'Pear'
x <- c("Fruit","Animal","Animal","Fruit","Fruit","Animal","Animal","Fruit")
y <- c("Pear","Dog","Cat","Apple","Banana","Monkey","Giraffe","Pear")
#bind x and y into a dataframe with two columns, using cbind() (column bind)
choices_table <- as.data.frame(cbind(x,y))
colnames(choices_table) <- c("category","items")
# look at the table of choices
# choices_table
# choices_table$category
```
```{r observeEvent, eval=TRUE, error=TRUE}
# start of inputPanel
inputPanel(
selectInput(inputId="choose_category",
label="Select category",
choices=unique(choices_table$category),
selected=unique(choices_table$category)[1]),
selectInput(inputId="choose_item",
label="Select item",
choices=unique(choices_table$items),
selected=unique(choices_table$items)[1])
#end of inputPanel
)
tableOutput("tb_chosen")
output$tb_chosen <- renderTable(subset(choices_table,choices_table$category==input$choose_category & choices_table$items==input$choose_item), rownames=TRUE, bordered = TRUE)
observeEvent(input$choose_category,
{updateSelectInput(session,
inputId="choose_item",
choices=unique(choices_table[choices_table$category == input$choose_category,"items"]))
}
)
```