How to make the variable to aggregate data frame columns by reactive? - r

Question

In the below MWE code and as shown in the image below, the aggregate() function is used to sum columns in a data frame. I'd like the user to be able to choose which variable to aggregate by, either Period_1 or Period_2 via clicking the radio button. Currently the below is coded only for Period_1.
How would I modify the $Period... in each aggregate() function, to reflect the user radio button input? So the user can also aggregate by Period 2 in this example.
MWE code:
library(shiny)
data <- data.frame(Period_1=c("2020-01","2020-02","2020-03","2020-01","2020-02","2020-03"),
Period_2=c(1,2,3,3,1,2),
ColA=c(10,20,30,40,50,60),
ColB=c(15,25,35,45,55,65)
)
ui <-
fluidPage(
h3("Data table:"),
tableOutput("data"),
h3("Sum the data table columns:"),
radioButtons(
inputId = 'vetaDataView2',
label = NULL,
choices = c('By period 1','By period 2'),
selected = 'By period 1',
inline = TRUE
),
tableOutput("totals")
)
server <- function(input, output, session) {
sumColA <- aggregate(data$ColA~Period_1,data,sum)
sumColB <- aggregate(data$ColB~Period_1,data,sum)
totals <- as.data.frame(c(sumColA, sumColB[2]))
colnames(totals) <- c("Period_1","Sum Col A","Sum Col B")
output$data <- renderTable(data)
output$totals <- renderTable(totals)
}
shinyApp(ui, server)

Answer 1

One option to achieve your desired result would be to use paste and as.formula to create the formula to aggregate your data base on the user input:
Note: To make my life a bit easier I switched to choiceNames and choiceValues.
library(shiny)
data <- data.frame(
Period_1 = c("2020-01", "2020-02", "2020-03", "2020-01", "2020-02", "2020-03"),
Period_2 = c(1, 2, 3, 3, 1, 2),
ColA = c(10, 20, 30, 40, 50, 60),
ColB = c(15, 25, 35, 45, 55, 65)
)
ui <-
fluidPage(
h3("Data table:"),
tableOutput("data"),
h3("Sum the data table columns:"),
radioButtons(
inputId = "vetaDataView2",
label = NULL,
choiceNames = c("By period 1", "By period 2"),
choiceValues = c("Period_1", "Period_2"),
selected = "Period_2",
inline = TRUE
),
tableOutput("totals")
)
server <- function(input, output, session) {
sumColA <- reactive({
fmlaA <- as.formula(paste("ColA", input$vetaDataView2, sep = " ~ "))
aggregate(fmlaA, data, sum)
})
sumColB <- reactive({
fmlaB <- as.formula(paste("ColB", input$vetaDataView2, sep = " ~ "))
aggregate(fmlaB, data, sum)
})
output$data <- renderTable(data)
output$totals <- renderTable({
totals <- as.data.frame(c(sumColA(), sumColB()[2]))
colnames(totals) <- c(input$vetaDataView2, "Sum Col A", "Sum Col B")
totals
})
}
shinyApp(ui, server)
#>
#> Listening on http://127.0.0.1:6231