Scatter plot with a categorical variable

[Poomthan Rangkakulnuwat]

I have three categorical variables (capacity, times, prices). The capacity has three levels ( 4 cups, 8 cups, and 10 cups). After run regression with these three categorical variables (capacity, times, prices), I have predicted values of preference (prefhat).
How can I have a scatter plot of prefhat against capacity (with three level) along with a connected line of average prefhat in each level of capacity? (The scatter plot and the line is in the same graph)
Thank You

[Nick Cox]

sysuse auto, clear
regress mpg i.foreign i.rep78
predict prehat
egen mean = mean(prehat), by(rep78)
scatter prehat rep78 || line mean rep78, sort

[Poomthan Rangkakulnuwat]

Thank you very much.