Persistent invalid graphics state error when using ggplot2

Question

I believe my dataframe is okay and my code is okay. In fact, I have eliminated parts of the dataframe and most of the graphing code to make things as basic as possible. But still, I get:

Error in .Call.graphics(C_palette2, .Call(C_palette2, NULL)) :    invalid graphics state 

What is wrong here? Here is the data:

 date   trt var val 1/8/2008    cc  sw5 0.2684138 1/8/2008    cc  sw15    0.2897586 1/8/2008    cc  sw5 0.2822414 2/8/2008    cc  sw5 0.2494583 2/8/2008    cc  sw5 0.2692917 2/8/2008    cc  sw15    0.2619167 2/8/2008    cc  sw5 0.204375 3/8/2008    cc  sw5 0.2430625 3/8/2008    cc  sw5 0.2654375 3/8/2008    cc  sw5 0.2509583 3/8/2008    cc  sw5 0.2055625 1/8/2008    ccw sw15    0.2212414 1/8/2008    ccw sw5 0.3613448 1/8/2008    ccw sw5 0.2607586 2/8/2008    ccw sw5 0.2087917 2/8/2008    ccw sw15    0.3390417 2/8/2008    ccw sw5 0.2436458 2/8/2008    ccw sw5 0.290875 3/8/2008    ccw sw5 0.20175 3/8/2008    ccw sw15    0.328875 3/8/2008    ccw sw5 0.2328958 3/8/2008    ccw sw5 0.2868958 

When I work with this data, I specify dates like this:

df<-df[order(as.Date(df$date,format="%d/%m/%Y")),,drop=FALSE] 

and here I want to make a scatterplot:

ggplot(data = df,aes(x = date,y = val)) +   geom_point(aes(group = trt)) 

Answer 1

I ran into this same error and solved it by running:

dev.off() 

and then running the plot again. I think the graphics device was messed up earlier somehow by exporting some graphics and it didn't get reset. This worked for me and it's simpler than reinstalling ggplot2.