Possible to pass a model to output in a shiny app? - r

Question

I would like to select a feature and model (from sidebar dropdown menu's) and be able to pass the model to a specific output where I print the summary of the model and show how well the model fits graphically. I currently have a reactive function in server.R that checks which input$model is selected, then fits the model and returns it. When I try to call this reactive function from output$evaluation I get errors. I'm not sure how to do this.
# server.R
#...
fitter <- reactive({
df_clean <- dataset() # another reactive function that selects the dataset to be used
rownames(df_clean) <- df_clean$timestamp
df_clean$timestamp <- NULL
if (input$Model == 'Linear'){
fit <- lm(input$Response ~., data=df_clean)
}
#... more if statements checking for other model types
return(fit)
})
# Model Evaluation
output$Evaluation <- renderPrint({
summary(fitter())
})

Answer 1

You can convert the string in your lm call to a formula, using as.formula.
library(shiny)
shinyApp(
shinyUI(
fluidPage(
inputPanel(
selectInput("Model", "Model:", choices=c("Linear", "Other")),
selectInput("Response", "Response:", choices=c("mpg", "disp"))
),
tableOutput("Evaluation")
)
),
shinyServer(function(input, output, session) {
fitter <- reactive({
df_clean <- mtcars
if (input$Model == 'Linear'){
fit <- lm(as.formula(paste(input$Response, "~.")), data=df_clean)
}
return(fit)
})
output$Evaluation <- renderTable({
summary(fitter())
})
})
)