non-numeric argument to binary operator [closed]

Answer 1

With version 2.0.0, ggplot2 has gained a new geometry, geom_blank() which draws nothing.

It can be used to avoid this type of errors when it is placed as last layer.

plot <- ggplot(data, aes(x, y)) +
  geom_point() +
  #aes(alpha=0.3,color=scale) +
  #scale_color_gradient(high="red") +
  geom_blank()

Using geom_blank() in this way is similar to the workaround in @krlmlr's answer which uses list() as last layer.