Creating facet from a single data frame in ggplot2

Question

How can I create a plot with different facet based on each column but still the same value of x base on the row names.

Let's say I have a summary from regsubsets() but since it returns a list I have to make it as a data frame first (is there anyway I can use ggplot2 with list?).

set.seed(1)
X = rnorm(100)
e = rnorm(100)
Y = 8 + 7*X + 2.5*X^2 - 9*X^3 + e
regfit.full = regsubsets(Y~poly(X,10,raw=T), data=data.all, nvmax=10)
(reg.summary = summary(regfit.full))

df = data.frame(reg.summary$cp, reg.summary$bic, reg.summary$adjr2)

> names(df)
[1] "reg.summary.cp"    "reg.summary.bic"   "reg.summary.adjr2"

> dim(df)
[1] 10  3

Now the question is how can I make a facet for each features (i.e. reg.summary.cp, reg.summary.bic, reg.summary.adjr2) that will be the value on the y-axis and the value for the x-axis will be the row number.

Answer 1

Could be done by adding rownumbers and melting the dataframe using reshape2:

library(reshape2)
library(ggplot2)

data.all = data.frame()

set.seed(1)

X = rnorm(100)
e = rnorm(100)
Y = 8 + 7 * X + 2.5 * X ^ 2 - 9 * X ^ 3 + e

regfit.full = regsubsets(Y ~ poly(X, 10, raw = T), data = data.all, nvmax = 10)
(reg.summary = summary(regfit.full))

df = data.frame(reg.summary$cp, reg.summary$bic, reg.summary$adjr2)
df$rownum <- 1:NROW(df)

molten_df <- melt(df, id.vars = "rownum")

ggplot(data = molten_df, aes(x = rownum, y = value)) +
  geom_point() +
  facet_wrap( ~ variable)

EDIT: maybe make the y-axes independet from one another by adding scales = "free_y" So:

ggplot(data = molten_df, aes(x = rownum, y = value)) +
  geom_point() +
  facet_wrap( ~ variable, scales = "free_y")

EDIT2: a way to make the plot without melting df:

grid.arrange(
  ncol = 3,
  ggplot(data = df) +
    geom_point(aes(x = rownum, y = reg.summary.cp)),
  ggplot(data = df) +
    geom_point(aes(x = rownum, y = reg.summary.bic)),
  ggplot(data = df) +
    geom_point(aes(x = rownum, y = reg.summary.adjr2))
)