selectInput not working when variables are selected - r

Question

Hopefully just a quick question, I have added in a selectInput function into my code and linked this to the server, however whenever I change the "year" within the app the scatterplot doesn't change the plots based on the year.
Am I missing some code?
library(shiny)
library(ggplot2)
pigs <- read.csv("pigs_data.csv")
# Define UI for application
ui <- fluidPage(
# Application title
titlePanel("Pig Breeding"),
sidebarLayout(
sidebarPanel(
#Allows user to choose a year which changes the distribution of plot points
selectInput(inputId = "year",
label = "Choose a year:",
choices = c(2016, 2017, 2018),
selectize = FALSE
)
),
# Show a plot of the generated distribution
mainPanel(
plotOutput("scatterplot")
)
)
)
# Define server logic
server <- function(input, output) {
output$scatterplot <- renderPlot({
input$year
ggplot(pigs,
aes(x = sow_count, y = species, col = species)) +
geom_point() +
facet_grid(. ~year)
})
}
# Run the application
shinyApp(ui = ui, server = server)

Answer 1

EDIT - before trying the observeEvent solution:
Depending on what exactly you want to plot it could be becaose of facet_grid(. ~year) and not facet_grid(. ~input$year).
If facet_grid(. ~input$year) is not what you are looking for, then ...
You can try the observeEvent from the shiny package:
observeEvent(input$year, {
output$scatterplot <- renderPlot({
input$year
ggplot(pigs,
aes(x = sow_count, y = species, col = species)) +
geom_point() +
facet_grid(. ~year)
})
})
Basically whenever the object input$year changes, you render a new plot.
Your example will look like this:
library(shiny)
library(ggplot2)
pigs <- read.csv("pigs_data.csv")
# Define UI for application
ui <- fluidPage(
# Application title
titlePanel("Pig Breeding"),
sidebarLayout(
sidebarPanel(
#Allows user to choose a year which changes the distribution of plot points
selectInput(inputId = "year",
label = "Choose a year:",
choices = c(2016, 2017, 2018),
selectize = FALSE
)
),
# Show a plot of the generated distribution
mainPanel(
plotOutput("scatterplot")
)
)
)
# Define server logic
server <- function(input, output) {
observeEvent(input$year, {
output$scatterplot <- renderPlot({
input$year
ggplot(pigs,
aes(x = sow_count, y = species, col = species)) +
geom_point() +
facet_grid(. ~year)
})
})
}
# Run the application
shinyApp(ui = ui, server = server)
I hope this works for you :)

Answer 2

I think that you need to update your table pigs if it contains the variable year like this:
server <- function(input, output) {
output$scatterplot <- renderPlot({
input$year
ggplot(pigs %>% filter(year %in% input$year),
aes(x = sow_count, y = species, col = species)) +
geom_point() +
facet_grid(. ~year)
})
}
Hope this help.