Shiny Concepts Without Runtime

Reactive Value

Recompute a Summary

Reactive expressions recompute derived values when their inputs change.

Program

Play the script to change the modeled input count and see the derived total update.

reactive_value.R 
input_count <- 
base <- c(5, 10, 15)
limit <- input_count * 3
filtered <- base[base <= limit]
total <- sum(filtered)
label <- paste("reactive", total, sep = ":")
cat(label, "\n", sep = "")

input_count <- 
base <- c(5, 10, 15)
limit <- input_count * 3
filtered <- base[base <= limit]
total <- sum(filtered)
label <- paste("reactive", total, sep = ":")
cat(label, "\n", sep = "")

input_count <- 
base <- c(5, 10, 15)
limit <- input_count * 3
filtered <- base[base <= limit]
total <- sum(filtered)
label <- paste("reactive", total, sep = ":")
cat(label, "\n", sep = "")
input dependency The derived limit depends on the selected input count.
reactive expression Filtering and summing model a reactive expression recomputing from inputs.
output value The final label is the value an output binding could display.