Plot with multiple lines in different colors using ggplot2

Question

I have a data frame consisting of a year column (1980-2009) and 16 columns with meteorological data from 16 different models. So each value represents the annual value for a year and a model. Here is some code to make it very easy to reproduce:

set.seed(20)
df <- as.data.frame(matrix(rnorm(120), 30, 16))
df[,17] <- 1980:2009
df <- df[,c(17,1:16)]
colnames(df) <- c("Year", "Model 1", "Model 2", "Model 3", "Model 4", "Model 5", "Model 6", "Model 7", "Model 8", 
                  "Model 9","Model 10", "Model 11", "Model 12", "Model 13", "Model 14", "Model 15", "Model 16")

Now I would like to plot it with ggplot2. The goal is to have one plot with multiple lines in different colors, each line representing a different model. Ideally, you should be able to select the color for each line.

I already checked out assumed similar questions like these two: Question1 Question2

But none of them really worked out with my example.

The result should look somewhat like this from Excel with the same data:

Anybody with a hint?

Answer 1

ggplot needs the data long instead of wide. You can use tidyr's pivot_longer, but there are other functions as well like reshape.

library(tidyverse)
set.seed(20)
df <- as.data.frame(matrix(rnorm(30*16), 30, 16))
df[,17] <- 1980:2009
df <- df[,c(17,1:16)]
colnames(df) <- c("Year", "Model 1", "Model 2", "Model 3", "Model 4", "Model 5", "Model 6", "Model 7", "Model 8", 
                  "Model 9","Model 10", "Model 11", "Model 12", "Model 13", "Model 14", "Model 15", "Model 16")
df %>% 
  as_tibble() %>% 
  pivot_longer(-1) %>% 
  ggplot(aes(Year, value, color = name)) + 
   geom_point() +
   geom_line() 

For a more interpolated line you can try ggalt's x-spline approach

df %>% 
  as_tibble() %>% 
  pivot_longer(-1) %>% 
  filter(grepl("12|13|14", name)) %>% 
  ggplot(aes(Year, value, color = name)) + 
  geom_point() +
  ggalt::geom_xspline()