Create graph based on selection of input and output - r

Question

New to shiny. I am trying to create a plot based on chosen x and y values. Basically, whatever the user selects for the select1 and select2 selectInput function will graph it accordingly. My original data has many columns, not just two. When I try to graph very specific things, my code works great, but when I try to graph what the user "selects" it does not work.
library(shiny)
library(readr)
library(ggplot2)
library(dplyr)
data0 <- rnorm(n = 10, mean = 100, sd = 5)
data1 <- rnorm(n = 10, mean = 50, sd = 10)
data2 <- data.frame(data0, data1)
attach(data2)
ui <- fluidPage(
selectInput(inputId = "select1",
label = "select the x-axis",
choices = c(" ", "data0", "data1")
),
selectInput(inputId = "select2",
label = "select the y-axis",
choices = c(" ", "data0", "data1")
),
submitButton(text = "Apply Changes", icon = NULL, width = NULL),
plotOutput(outputId = "myplot")
)
server <- function(input, output) {
output$myplot <- renderPlot({
data2 %>%
ggplot(aes(input$select1 ~ input$select2))+
geom_point(alpha = 0.8)
})
}
shinyApp(ui = ui, server = server)

Answer 1

I had to add ggplot(aes(x = get(paste(input$select1)), y = get(paste(input$select2)) to make the input selects work.
library(shiny)
library(readr)
library(ggplot2)
library(dplyr)
data0 <- read_csv("DeltaX_Soil_Properties_Fall2020_Spring2021_Fall2021.csv")
data1 <- data0[!(data0$time_marker_sampled == "-9999"),]
attach(data1)
ui <- fluidPage(
selectInput(inputId = "select1",
label = "select the x-axis",
choices = c(" ", "elevation_navd88", "sediment_accretion", "days_between_sampling_and_deployment", "normalized_accretion", "soil_bulk_density", "soil_organic_matter_content", "soil_organic_carbon", "soil_organic_carbon_density")
),
selectInput(inputId = "select2",
label = "select the y-axis",
choices = c(" ", "elevation_navd88", "sediment_accretion", "days_between_sampling_and_deployment", "normalized_accretion", "soil_bulk_density", "soil_organic_matter_content", "soil_organic_carbon", "soil_organic_carbon_density")
),
submitButton(text = "Apply Changes", icon = NULL, width = NULL),
plotOutput(outputId = "myplot")
)
server <- function(input, output) {
output$myplot <- renderPlot({
data1 %>%
ggplot(aes(x = get(paste(input$select1)), y = get(paste(input$select2)), col = hydrogeomorphic_zone))+
geom_point(alpha = 0.8)
})
}
shinyApp(ui = ui, server = server)

Answer 2

If you want to use a variable as x or y, you can alternatively use aes_() instead of aes().
This would then result in:
ggplot(aes_(x = input$select1, y = input$select2))
Beware, that you need to add a tilde if you want to use a normal column name with aes_(), e.g.:
ggplot(aes_(x = ~elevation_navd88, y = input$select2))