CODEWITHSUNDEEP
rggplot2
Scott Morken
Scott Morken

Reputation: 1651

ggplot2 plotting a single value in a bar graph

I am plotting multiple bar graphs to compare the values in data of this type this is the contents of df4 where combinations of time_step and disturbance_type will be unique. I am doing this for data qaqc, and this is a small sample of the data I have.

time_step   disturbance_type_id variable    value
1   1   difference  8.040223e+01
10  1   difference  5.520571e+01
11  1   difference  2.145634e+02
12  1   difference  7.351697e+01
13  1   difference  6.682899e+00
14  1   difference  4.242542e+01
15  1   difference  2.102968e+01
16  1   difference  3.772944e+01
17  1   difference  6.365049e+01
1   2   difference  6.365049e+01

The code i am using to plot it is 

differencePlot <- function(distTypeID)
{
  p<-ggplot(data=df4[df4[2]==distTypeID,], aes(x=time_step, y=value, fill=value)) +
    geom_bar(position="dodge",stat="identity") +
    ylab("percent difference in disturbance area") +
    ggtitle(paste("disturbance type ", distTypeID))  

  ggsave(filename=paste("disturbancesByTimeStepAndProject\\", "disturbance_area_differences_", distTypeID, ".png", sep=""), plot=p )
}

lapply(unique(df4$disturbance_type_id), function(x) differencePlot(x))

So I am essentially creating 1 bar graph file for each disturbance unique type id. When the function is called, and multiple rows of timesteps exist within the given disturbance_type_id all is well, but when the function is called with distTypeID = 2 (where only a single row of data will exist), the function fails with this error message. 

 Error in grid.Call.graphics(L_raster, x$raster, x$x, x$y, x$width, x$height,  : 
   Empty raster

Is it not possible to graph with a single bar? Any ideas?

Upvotes: 2

Views: 2964

Answers (1)

eipi10
eipi10

Reputation: 93761

This appears to be a known bug in ggplot2. You can work around it by creating an if ... else statement in your function that checks for a single row of data. In that case you'll want your code to set the bar color outside of aes. For example:

p <- ggplot(data=df4[df4[2]==distTypeID,], aes(x=time_step, y=value)) +
       geom_bar(position="dodge",stat="identity", fill="blue") +
       ylab("percent difference in disturbance area") +
       ggtitle(paste("disturbance type ", distTypeID))

Upvotes: 1

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