How to put lines on a chart and bar?

Question

I’d like to know how to insert lines in a bar graph.

I have the following code:

Periodo <- c("01/2020", "03/2020", "05/2020",
            "06/2020", "08/2020", "09/2020")
Valores <- c("0,08", "3,15", "4,91", "0,72", "6,21", "8,80")

teste <- data.frame(Periodo, Valores)

library(ggplot2)

ggplot(teste) + aes(x = Periodo, y = Valores) + geom_bar(stat='identity')

Answer 1

I’d like to know how to insert lines in a bar graph.

You can insert lines using geom_line():

ggplot(teste, aes(x = Periodo, y = Valores, group = 1)) + 
  geom_bar(stat='identity') +
  geom_line()

Answer 2

The main problem seems to be the vector Valores be a class vector "character", the numbers are strings, without any numerical value. This can be seen by the yy axis, whose annotations are equidistant although the values are not equidistant. Differences from one value to the other are not constant but the difference in bar heights is always the same.

To have the right graph, you have to transform the vector Valores in numerical vector, replacing first the commas with dots.

The final chart shows the two charts side by side with the package gridExtra, in order to better see the difference.

library(ggplot2)

Periodo <- c("01/2020", "03/2020", "05/2020",
             "06/2020", "08/2020", "09/2020")
Valores <- c("0,08", "3,15", "4,91", "0,72", "6,21", "8,80")

teste <- data.frame(Periodo, Valores)

g1 <- ggplot(teste, aes(x = Periodo, y = Valores, group = 1)) + 
  geom_bar(stat='identity') +
  geom_line() +
  ggtitle("Gráfico original")

Valores <- as.numeric(sub(",", ".", Valores))
teste <- data.frame(Periodo, Valores)

g2 <- ggplot(teste, aes(x = Periodo, y = Valores, group = 1)) + 
  geom_bar(stat='identity') +
  geom_line() +
  ggtitle("Gráfico depois de 'as.numeric/sub'")

gridExtra::grid.arrange(g1, g2, nrow = 1, ncol = 2)