Plot time series on defined scale

Question

I have a time series record, and I’m having trouble plotting on an appropriate scale. Take this example:

#Gerar sinal v1     
v1=sin(seq(from=0, to=3*2*pi, length=11060))

#Gerar sinal v2
v2=sin(seq(from=0, to=5*2*pi, length=11060))

#Gerar série temporal horária entre 06-maio-2016 15h:00min e 10-ago-2017 10h:00min
time_series_total <- seq(from = as.POSIXct("2016-05-06 15:00"),
                         to = as.POSIXct("2017-08-10 10:00"), by = "hour") 

So when I plot:

plot(x = time_series_total, y = v1, type = 'l', col = "red", xlab = "tempo")
    lines(x = time_series_total, y = v2, col = 'blue')
    legend("topright", legend=c("v1", "v2"),
           col=c("red", "blue"), lty=1:1, cex = 1.25, box.lty=0,inset = 0.005)

... The abscissa scale is not legal

:

What I would like to do is present the scale of the axes with the information of month and year. What is the suggestion?

Answer 1

For me, the issue of axis Labels is easier to solve using the package ggplot2 to chart. For this, you must first prepare your data so that it is in three columns:

• sinal, with the values of each signal, one after the other

• tempo, with the time values for each signal, which implies that this column will have n values, but only n/2 distinct, as it is necessary that the same time occurs for each signal

• grupo, which will identify if the observation refers to each value of sinal belongs to the group v1 or v2

Assuming that the data has already been generated according to the question, the code below does this as listed above, placing the results in a data frame called dados:

sinal <- c(v1, v2)
tempo <- rep(time_series_total, 2)
grupo <- rep(c("v1", "v2"), each=length(v1))

dados <- data.frame(sinal, tempo, grupo)

Next, just use the packages ggplot2 and scales to generate the desired chart:

library(ggplot2)
library(scales)
ggplot(dados, aes(x=tempo, y=sinal, colour=grupo)) +
  geom_line() +
  scale_x_datetime(labels=date_format("%B/%Y")) +
  labs(x="Data", y="Sinal", colour="Grupo")

I recommend seeing the help of the function scale_x_datetime if you want to change the intervals between the Abels or their format.

Answer 2

plot(time_series_total, v1, type = 'l', col = "red", xlab = "tempo", xaxt = "n")
lines(x = time_series_total, y = v2, col = 'blue')
legend("topright", legend=c("v1", "v2"), col=c("red", "blue"), lty=1:1, cex = 1.25, box.lty=0,inset = 0.005)

r <- as.POSIXct(round(range(time_series_total), "days"))
axis.POSIXct(1, at = seq(r[1], r[2], by = "month"), format = "%Y-%m")