[R] Need help plotting

[Rui Barradas]

Hello,

This type of problems generally has to do with reshaping the data. The 
format should be the long format and the data is in wide format.

Inline.

Às 23:35 de 21/09/2022, DFP escreveu:
> As I said, the lines below that you provided worked well for me. Can you 
> explain what this line does?:
> 
> # reshape to long format
>     pivot_longer(-Dtime, names_to = "NO2") %>%
> 
> -------------------------------------------------
> 
> library(ggplot2)
> library(dplyr)
> library(tidyr)
> 
> b %>%
>     mutate(Dtime = paste(Sys.Date(), Dtime),
>                   Dtime = as.POSIXct(Dtime)) %>%
>     select(Dtime, DNO2, MNO2) %>%
>     # reshape to long format
>     pivot_longer(-Dtime, names_to = "NO2") %>%


After selecting only the columns Dtime and *NO2 you need to reshape the 
data to long format. Some ways of telling pivot_longer what are the 
columns to become one are

  - explicitly writing all columns to be pivotted;
  - with negative indexing, all others will be put under the new name "NO2";
  - with a selection function such as ends_with("NO2"). This is probably 
more readable code if you return to it some time from now.


     pivot_longer(ends_with("NO2"), names_to = "NO2") %>%


With data in the long format map column NO2 to the color aesthetic and 
ggplot will automatically understand that you have 2 groups, DNO2 and 
MNO2, and plot 2 lines and 2 groups of points (one for each color) .

Hope this helps,

Rui Barradas


>     # now plot
>     ggplot(aes(Dtime, value, color = NO2)) +
>     geom_line() +
>     geom_point() +
>     scale_color_manual(values = c("orange", "skyblue")) +
>     # make datetime labels
>     scale_x_datetime(date_breaks = "1 mins", date_labels = "%H:%M") +
>     theme_bw()
> 
>