使用GGPlot在同一图上绘制多条线时遇到麻烦[包含数据集]

Question

Here is the data set, df.test:

   MLSpredictions BPLPredictions
1        1.392213      0.8326201
2        1.392213      0.8662049
3        1.448370      0.9011444
4        1.448370      1.0146486
5        1.448370      0.9374932
6        1.448370      0.9374932
7        1.448370      0.9011444
8        1.448370      1.0981538
9        1.448370      1.0555757
10       1.506792      1.0555757
11       1.506792      1.1424492
12       1.506792      1.0555757
13       1.567570      1.0981538
14       1.567570      1.0981538
15       1.567570      1.1424492
16       1.567570      1.1424492
17       1.567570      1.1885314
18       1.567570      1.1424492
19       1.567570      1.1885314
20       1.630800      1.2364723

I know that GGPlot requires you to include all of the information in the same data frame which I believe I have done above.

Here is my starting point:

ggplot(df.test, aes(x = 1:20, y = , color = ))

Since my column names are different, I'm not sure what to put for "y". I've been looking all over for sample data frames that would be used in this instance but I'm coming up empty.

Please advise.

[EDIT] I would like to come up with a plot that has two lines with two different colors in the same plot.

Answer 1

ggplot expects the input data to be in so-called "long" format. In a long data set, 1 column contains the actual data values (whatever they may be), and all other columns tell us characteristics of those data points, such as what type of measure the values might be, what group they're a part of, etc. A long version of your data might look like:

index         variable      value
    1   MLSpredictions   1.392213
    2   MLSpredictions   1.392213
  ...              ...        ...
    1   BPLPredictions  0.8326201
    2   BPLPredictions  0.8662049
  ...              ...        ...

And you could then get your intended plot with:

my.plot <- ggplot(data = long.data, aes(x = index, y = value, color = variable)) +
           geom_line()

There are a few ways to convert your "wide" data into long format, one of which would be:

library(dplyr)
library(tidyr)

df$index <- 1:20
long.data <- gather(df, variable, value, -index)