ggplot2 differences between local and Shiny-hosted output

Question

I've noticed an unexpected difference in the rendering of a ggplot between local output and a Shiny application. The axes labels are entirely different:

Local: Shiny App:

The axes of the two plots differ by exactly 1 day - how very odd! What happened during the publishing to Shiny process?

Data

data.df <- structure(list(Report.Date = structure(c(1430434800, 1433026800, 
1435618800, 1438297200, 1440975600, 1443567600, 1430434800, 1433026800, 
1435618800, 1438297200, 1440975600, 1443567600), tzone = "", class = c("POSIXct", 
"POSIXt")), variable = structure(c(1L, 1L, 1L, 1L, 1L, 1L, 2L, 
2L, 2L, 2L, 2L, 2L), .Label = c("Datasets.Deposited", "Datasets.Published"
), class = "factor"), value = c(0L, 21L, 32L, 43L, 56L, 73L, 
0L, 4L, 9L, 21L, 29L, 49L)), .Names = c("Report.Date", "variable", 
"value"), row.names = c(NA, -12L), class = "data.frame")

Local code

library(ggplot2)
library(scales)
base <- ggplot(data.df, aes(Report.Date, value))
plot <- base + geom_area(aes(group = variable, fill= variable), position = 'identity') + geom_point(aes(color = series), color = "black")
plot <- plot + xlab("Date") + ylab("Number of Deposits/Published")
plot  +
  scale_y_continuous(breaks = seq(0,round(max(data.df$value)+5,-1),5)) +
  scale_x_datetime(breaks = date_breaks("1 month"), labels = date_format("%Y-%b-%d"), minor_breaks = "1 month") + 
  theme(axis.text.x = element_text(angle = 45, hjust = 1))

Shiny

ui.R

shinyUI(
  fluidPage(
    plotOutput("plot")
  )
)

server.R

library(ggplot2)
library(scales)
shinyServer(
  function(input, output){
    output$plot <- renderPlot({
      data.df <- 
      base <- ggplot(data.df, aes(Report.Date, value))
      plot <- base + geom_area(aes(group = variable, fill= variable), position = 'identity') + geom_point(aes(color = series), color = "black")
      plot <- plot + xlab("Date") + ylab("Number of Deposits/Published")
      plot  +
        scale_y_continuous(breaks = seq(0,round(max(data.df$value)+5,-1),5)) +
        scale_x_datetime(breaks = "1 month", labels = date_format("%d-%b-%Y"), minor_breaks = "1 month") + 
        theme(axis.text.x = element_text(angle = 45, hjust = 1))
    }
    )
  }
)

Mirek Długosz · Accepted Answer · 2015-10-07 22:51:38Z

4

1430434800 seconds since Unix epoch is 30 Apr 2015 23:00:00 GMT, which is dangerously close to end of the day.

When tz argument to as.POSIX* functions is missing or empty string, current (machine-dependent) timezone will be used.

It seems that you are currently at GMT or west, while R Shiny server is at GMT+1 or east. These two computers evaluate the same fixed point in time into different "wall-clock" times, and since reference point is close to midnight, there is artificial change of date.

To fix that, you should provide timezone definition, so POSIX* functions don't have to fallback to unpredictable default.

Looks like you can do that by giving tzone property an "GMT" value:

data.df <- structure(list(Report.Date = structure(c(1430434800, 1433026800, 1435618800, 1438297200, 1440975600, 1443567600, 1430434800, 1433026800, 1435618800, 1438297200, 1440975600, 1443567600), tzone = "GMT", class = c("POSIXct", "POSIXt")), …

answered Oct 7, 2015 at 22:51

Mirek Długosz

4,3053 gold badges26 silver badges41 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Charlotte Hadley Over a year ago

Great! Thanks, I'll look into this - as you saw I'm GMT, so I'll try this in the morning.

Charlotte Hadley Over a year ago

This worked for me - I think it's useful to note there was an issue on ggplot2 about "scale_x_datetime converts POSIXct to local timezone" that I found aftet you gave me the hat tip to timezones being the issue - github.com/hadley/ggplot2/issues/533

Collectives™ on Stack Overflow

ggplot2 differences between local and Shiny-hosted output

Data

Local code

Shiny

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

Data

Local code

Shiny

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related