[R] ggplot2: 'not finding <-<- error'

[Rich Shepard]

I'm writing a script to plot data distributions. It worked in a basic form
and I'm now adding features and tweaking the presentation. When I sourced
the file this error appeared:

Error in p1 <- ggplot(data = pdx_disc, aes(x = NULL, y = cfs)) + geom_boxplot(color = "#00008B",  (from all_disc_boxplot.r#9) :
   could not find function "<-<-"

Line 9 in the script defines the first boxplot:
p1 <- ggplot(data = pdx_disc, aes(x = NULL, y = cfs)) +
     geom_boxplot(
         # custom boxes
         color='#00008B',
         fill='#00008B',
         alpha=0.2,
         # custom outliers
         outlier.color='#B22222',
         outlier.fill='#FF3030',
         outlier.size=2) +
     coord_flip() +
     xlab = 'Portland Discharge'

I don't see any <-<- (nor have I before now) and I need help understanding
the source of this error.

TIA,

Rich