ggplot2 geom_smooth with variable as factor

Question

I have a small issue, which I can ridiculously not solve myself.

I have a simple data frame, which I want to plot with ggplot2. When I use the variable weight as a factor I get all values in the x-axis, s. plot 2, but not when I use it as integer, s. plot 1. However, I want to use geom_smooth, which seems to function only with plot 1, but not in plot 2 where weight is a factor.

How do I get a graph in ggplot2, which shows me all values of weight and additionally the geom_smooth function?

Consider this example file:

require(ggplot2)

x <- get.url(https://dl.dropboxusercontent.com/u/109495328/example.csv)
app_df <- read.csv(x, header=T, sep = ",", quote = "", stringsAsFactors = FALSE, na.strings = "..")     
colnames(app_df) <- c("Date", "Weight")

date <- as.Date(strptime(app_df$Date, "%d.%m.%Y"))
weight <- app_df$Weight
df <- na.omit(data.frame(date,weight))

# plot 1 (only few values indicated in x axis)
ggplot(df, aes(date,weight)) +
  geom_point() +
  geom_line(aes(group = "1")) +
  geom_smooth(method = "lm")

# plot 2 (no smooth function)
ggplot(df, aes(date,as.factor(weight))) +
  geom_point() +
  geom_line(aes(group = "1")) +
  geom_smooth(method = "lm")

Answer 1

Is this what you are after?

require(ggplot2)

x <- url("https://dl.dropboxusercontent.com/u/109495328/example.csv")
app_df <- read.csv(x, header=T, sep = ",", quote = "", stringsAsFactors = FALSE, na.strings = "..")     
colnames(app_df) <- c("Date", "Weight")

date <- as.Date(strptime(app_df$Date, "%d.%m.%Y"))
weight <- app_df$Weight
df <- na.omit(data.frame(date,weight))

# plot 1 (only few values indicated in x axis)
ggplot(df, aes(date,weight)) +
  geom_point() +
  geom_line(aes(group = "1")) +
  geom_smooth(method = "lm")

# plot 2 (no smooth function)
ggplot(df, aes(date,as.numeric(as.factor(weight)))) +
  geom_point() +
  geom_line(aes(group = "1")) +
  geom_smooth(method = "lm")