How can I shorten or summarise my command?

Question

i'm currently writing a code in R and I need a visualization of the data. Its about EDA data. In the rows I have the different samples (points of measurement) and every column is the data of one subject(V1, V2...). I tried many things and now did it with ggplot:

ggplot()+
  geom_line(data = eda_pos_z, aes(x=1:nrow(eda_pos_z), y=V1, col = "VP1")) + 
  geom_line(data = eda_pos_z, aes(x=1:nrow(eda_pos_z), y=V2, col = "VP2")) +   
  geom_line(data = eda_pos_z, aes(x=1:nrow(eda_pos_z), y=V3, col = "VP3")) +
  geom_line(data = eda_pos_z, aes(x=1:nrow(eda_pos_z), y=V4, col = "VP4")) +
  geom_line(data = eda_pos_z, aes(x=1:nrow(eda_pos_z), y=V5, col = "VP5")) +
  geom_line(data = eda_pos_z, aes(x=1:nrow(eda_pos_z), y=V6, col = "VP6")) +
  ylab('EDA') +
  xlab('samples')

With this I have all data lines in one graph but the problem is that I have 49 columns (so this is just an extract) and i guess there is a better/shorter way to achieve what i need. I just don't know how. Can anybody help me?

Thanks and sorry for possible spelling mistakes, Luisa :)

Answer 1

The following should work, and is the way ‘ggplot2’ is intended to be used:

eda_pos_z %>%
    mutate(x = row_number()) %>%
    pivot_longer(matches('^VP'), names_to = 'name', values_to = value) %>%
    ggplot() +
    geom_line(aes(x = x, y = value, color = name) + 
    ylab('EDA') +
    xlab('samples')

That is, the data from the VP* columns is first transformed into long form (aka “tidy data”), which puts the names into columns. Furthermore, aesthetics are usually based on variables, not on values (such as your manually created x-values).

(The above uses the packages ‘dplyr’ for mutate, and ‘tidyr’ for pivot_longer … other ways of achieving the same result exists, including in base R, but these two packages are worth learning/using anyway.)