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I am attempting to create a ggplot in shiny that responds to user-defined input related to date. Seems like a straight forward problem and one that I've successfully accomplished before.

In this problem, I have values for MODIS in the dataframe weatherYear that the user is selecting. Each 16 calendar days is a distinct MODIS value (e.g., Jan 1-16 = 1, Jan 17-Feb 1 = 2, and so forth. This reveals weather data in similar time increments as satellite imagery shown in another window of my shiny app.

If I use the following code in R (adapted as necessary), and vary the MODIS value, the graphs come out perfectly.

output$weather <- renderPlot({
  weatherData <- filter(weatherYear, weatherYear$MODIS <= input$index)
  ggplot(weatherData, aes(x=DOY), order = DOY) +
    geom_ribbon(aes(ymin = TempMin, ymax = TempMax), alpha = 0.3, fill = "indianred2") +
    geom_line(aes(y = TempAvg), color = "black") +
    geom_bar(aes(y = Precip*20), stat = "identity", color = "blue") +
    labs(y = "Mean Daily Temperature (F)", x = "Month") +
    coord_cartesian(ylim = c(-5,105), xlim = c(1, 365)) +
    scale_y_continuous(sec.axis = sec_axis(~./20, name="Precipitation (in)")) +
    scale_x_continuous(expand = c(0, 0),
      breaks = c(15,45,75,105,135,165,195,228,258,288,320,350),
     labels = c("J", "F", "M", "A", "M", "J", "J", "A", "S", "O", "N", "D"))

In shiny, the default value of 1 shows perfectly:

Shiny ggplot for default MODIS period

However, as soon as another index period is selected, a large gap is introduced and additional non-selected index values are graphed:

Same ggplot when MODIS index value of 2 is selected

I'm stumped...

zx8754
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Shawn Hutchinson
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    Possible duplicate or relevant post: https://stackoverflow.com/questions/14821064/line-break-when-no-data-in-ggplot2 – zx8754 Nov 14 '17 at 20:13
  • There is no line break or missing data in this case. Just a large gap is introduced when changing from the first index period (DOY 1-16) to the second (DOY 16-32). – Shawn Hutchinson Nov 15 '17 at 15:49

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