R: “Unary operator error” from multiline ggplot2 command

Question

I\'m using ggplot2 to do a boxplot comparison of two different species, as indicated by the third column shown below:

> library(reshape2)
> library(ggp         


        

Answer 1

It's the '+' operator at the beginning of the line that trips things up (not just that you are using two '+' operators consecutively). The '+' operator can be used at the end of lines, but not at the beginning.

This works:

ggplot(combined.data, aes(x = region, y = expression, fill = species)) +
geom_boxplot() 

The does not:

ggplot(combined.data, aes(x = region, y = expression, fill = species))
+ geom_boxplot() 

*Error in + geom_boxplot():
invalid argument to unary operator*

You also can't use two '+' operators, which in this case you've done. But to fix this, you'll have to selectively remove those at the beginning of lines.