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Construct a "reactive value" object
- The reactiveVal function is used to construct a "reactive value" object. This is an object used for reading and writing a value, like a variable, but with special capabilities for reactive programming.
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The reactiveVal function is used to construct a "reactive value" object. This is an object used for reading and writing a value, like a variable, but with special capabilities for reactive programming.
- 5 Reactive functions | Building Web Apps with R Shiny
Reactivity is how Shiny determines which code in server()...
- 5 Reactive functions | Building Web Apps with R Shiny
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The reactiveValfunction is used to construct a "reactive value"object. This is an object used for reading and writing a value, like avariable, but with special capabilities for reactive programming. When youread the value out of a reactiveVal object, the calling reactive expressiontakes a dependency, and when you change the value, it notifies any r...
reactiveVal is very similar to reactiveValues(), exceptthat the former is for a single reactive value (like a variable), whereas thelatter lets you conveniently use multiple reactive values by name (like anamed list of variables). For a one-off reactive value, it's more natural touse reactiveVal. See the Examples section for an illustration.
A function. Call the function with no arguments to (reactively) readthe value; call the function with a single argument to set the value.
- An optional initial value.
Reading a file when it changes is a common task, so Shiny provides an even more specific helper that just needs a file name and a reader function: server <- function ( input , output , session ) { data <- reactiveFileReader ( 1000 , session , "data.csv" , read.csv ) }
Mar 31, 2022 · Reactivity is how Shiny determines which code in server() gets to run when. Some types of objects, such as the input object or objects made by reactiveValues(), can trigger some types of functions to run whenever they change. For our example, we will use the reactive_demo app.
Sep 11, 2016 · One significant difference is that a reactiveValue is a container that can have several values, like input$. In shiny documentation functionality is usually implemented using reactive(), but in most cases I find reactiveValues() more convenient.
We’ll start with a survey of the server function, discussing in more detail how the input and output arguments work. Next we’ll review the simplest form of reactivity (where inputs are directly connected to outputs), and then discuss how reactive expressions allow you to eliminate duplicated work.
Wraps a normal expression to create a reactive expression. Conceptually, a reactive expression is a expression whose result will change over time.
