从日期列中提取年份 R Shiny 过滤器输入

Question

I am building a Shiny app and have to extract year from date column to create a slider with years. I have a column called date in format YYYY MM DD , trying to extract only the year in the filter part, but it doesn't work as expected. I am stuck at the following code:

 server <- function(input, output){ 
  data <- reactive({                
    ufo %>%                  
      filter(date >= format(as.Date(input$years[1],"%Y")),
             date <= format(as.Date(input$years[2], "%Y"))) 
  })

The error I get is:

Problem with filter() input..1.

[34mℹ[39m Input..1 is date >= format(as.Date(input$years[1], "%Y")).

[31mx[39m character string is not in a standard unambiguous format

How can I extract only the year for my filter?

Answer 1

Welcome to stackoverflow, it is always important to ask with a minimal reproducible example of your data, that way we can help you faster.

To do so, you can simulate one or share a fragment of yours.

Here one with what I think you have

library(shiny)
library(dplyr)
library(lubridate)

# Creating a minimal reproducible example of the data
set.seed(123)
ufo <- data.frame(
  date = sample(seq(as.Date('2010-01-01'), as.Date('2022-01-01'), by = 'day'), 20),
  ufo = sample(1:15, 20, replace = TRUE)
) %>%
  arrange(date)

#>          date ufo
#> 1  2011-06-10  11
#> 2  2012-08-10   9
#> 3  2012-10-13  10
#> 4  2013-02-15  15
#> 5  2013-12-20   5
#> 6  2014-06-15   7
#> 7  2014-11-25   7
#> 8  2015-01-16  12
#> 9  2015-07-06   7
#> 10 2016-02-05   1
#> 11 2016-09-28   4
#> 12 2016-11-15  14
#> 13 2017-01-10  12
#> 14 2017-07-19   9
#> 15 2017-11-27  11
#> 16 2018-03-05   5
#> 17 2019-03-25  10
#> 18 2019-06-08  13
#> 19 2021-09-30   7
#> 20 2021-10-16   5

Now that we have the data, let's move to the shiny part. It is good as well to include the minimal elements of your app, in this case I put a slider input the server using it.

The problem with your original code is that format() returns a character and you are comparing that with a date, which do not make sence. It is a better approach to extract the year of your date as numeric using lubridate::year() and compare that with the slider input values.

# User interface
ui <- fluidPage(
  sliderInput('year', 'Year', min = 2010, max = 2022, 
              step = 1, value = c(2015, 2020), sep = ''),

  dataTableOutput('table')
)

server <- function(input, output, session) {
    data <- reactive({
      ufo %>%
        filter(year(date) >= input$year[1], year(date) <= input$year[2])
    })
    
    output$table <- renderDataTable({
      data()
    })
}

^{Created on 2022-02-14 by the reprex package (v2.0.1)}