Object Not Found Error with Ggplot2

ggplot object not found error when adding layer with different data

Aesthetic mapping defined in the initial ggplot call will be inherited by all layers. Since you initialized your plot with color = GROUP, ggplot will look for a GROUP column in subsequent layers and throw an error if it's not present. There are 3 good options to straighten this out:

Option 1: Set inherit.aes = F in the layer the you do not want to inherit aesthetics. Most of the time this is the best choice.

ggplot(dummy,aes(x = X, y = Y, color = GROUP)) + 
  geom_point() +
  geom_segment(aes(x = x1, y = y1, xend = x2, yend = y2),
               data = df,
               inherit.aes = FALSE) 

Option 2: Only specify aesthetics that you want to be inherited (or that you will overwrite) in the top call - set other aesthetics at the layer level:

ggplot(dummy,aes(x = X, y = Y)) + 
  geom_point(aes(color = GROUP)) +
  geom_segment(aes(x = x1, y = y1, xend = x2, yend = y2),
               data = df) 

Option 3: Specifically NULL aesthetics on layers when they don't apply.

ggplot(dummy,aes(x = X, y = Y, color = GROUP)) + 
  geom_point() +
  geom_segment(aes(x = x1, y = y1, xend = x2, yend = y2, color = NULL),
               data = df) 

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Which to use?

Most of the time option 1 is just fine. It can be annoying, however, if you want some aesthetics to be inherited by a layer and you only want to modify one or two. Maybe you are adding some errorbars to a plot and using the same x and color column names in your main data and your errorbar data, but your errorbar data doesn't have a y column. This is a good time to use Option 2 or Option 3 to avoid repeating the x and color mappings.)

Object not found in ggplot

I don't think you need the scale_x_continuous, since (1) it's discrete, so (2) we can factor the data.

ggplot(BOTTRP, aes(factor(Chatbot), Mean, colour = Scale))+
  geom_point(size = 2)+
  labs(y = "Mean of chatbot evaluation", size=3)+
  theme_gray()+
  expand_limits(x=1:10, y=1:5)

R: Object not found with ggplot

This is similar to the other answer but without needless dplyr mumbo-jumbo and pointing out some important details. The point is that if you want manual colors, you should use a manual color scale.

mycol = c("#A38FCC","#7F40FF")
mynam = c("random_line1", "random_line2")
set.seed(123)
df=data.frame(
              #month needs to be an ordered factor to get correct order in the plot
              #an unordered factor would be ordered alphabetically by ggplot2
              month = ordered(month.abb, levels = month.abb), 
              mpft  = c(rep(1,6),rep(2,6)), 
              ran = runif(12,0.,10.))

library(ggplot2)

ggplot(df, aes(x=month,y=ran, 
               colour = factor(mpft) #you want a discrete color scale
               )) +
  geom_line(aes(group = mpft), size = 1) +
  scale_colour_manual(name = "mynam",
                      #always pass named character vectors here to ensure correct mapping
                      values = setNames(mycol, unique(df$mpft)), 
                      labels = setNames(mynam, unique(df$mpft))) 

ggplot geom_rect() error object not found

You just have an extra step of setting up a dataframe in geom_rect which coincide with data in ggplot. Simply provide your max and min values to geom_rect and it works:

ggplot(df, aes(Month, Value, group = 1)) + 
  geom_line() + 
  theme_minimal() + 
  geom_rect(aes(xmin = min(as.integer(Month)) - 0.5, 
                xmax = max(as.integer(Month)) + 0.5, 
                ymin = min(Value), 
                ymax = max(Value)),
            alpha = 0.2/nrow(df), fill = "green")

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