How to take the average of the values and make a dotted line graph, and change the polyline to a smooth curve? And add the legend?

Question

I tried to take the average of SF_Plante_Verte and SF_Plante_Totale acccording to their Date_obs.

df<-structure(list(Pos_heliaphen = c("X47", "W17", "Z17", "X47", 
                                     "Y19", "Y40", "X47", "Y19", "Y40", "Z17", "Z31", "X47", "Y19", 
                                     "Y40", "Z31", "X47", "Z17", "Z31"), traitement = c("WW", "WW", 
                                                                                        "WW", "WW", "WW", "WW", "WW", "WW", "WW", "WW", "WW", "WW", "WW", 
                                                                                        "WW", "WW", "WW", "WW", "WW"), Variete = c("Blancas", "Blancas", 
                                                                                                                                   "Blancas", "Blancas", "Blancas", "Blancas", "Blancas", "Blancas", 
                                                                                                                                   "Blancas", "Blancas", "Blancas", "Blancas", "Blancas", "Blancas", 
                                                                                                                                   "Blancas", "Blancas", "Blancas", "Blancas"), Date_obs = c("D11_04/06/2021", 
                                                                                                                                                                                             "D11_04/06/2021", "D11_04/06/2021", "D12_07/06/2021", "D12_07/06/2021", 
                                                                                                                                                                                             "D12_07/06/2021", "D23_25/06/2021", "D23_25/06/2021", "D23_25/06/2021", 
                                                                                                                                                                                             "D23_25/06/2021", "D23_25/06/2021", "D24_28/06/2021", "D24_28/06/2021", 
                                                                                                                                                                                             "D24_28/06/2021", "D24_28/06/2021", "D25_29/06/2021", "D25_29/06/2021", 
                                                                                                                                                                                             "D25_29/06/2021"), SF_Plante_Totale = c(46473, 44589.3, 43134, 
                                                                                                                                                                                                                                     166645.5, 119962.5, 93061.5, 483583.8, 313985.7, 273432.6, 414871.8, 
                                                                                                                                                                                                                                     426766.2, 539410.2, 337417.5, 273432.6, 474915, 539410.2, 414871.8, 
                                                                                                                                                                                                                                     474915), SF_Plante_Verte = c(46473, 44589.3, 43134, 162512.7, 
                                                                                                                                                                                                                                                                  119962.5, 93061.5, 462655.2, 293367.9, 238373.1, 363123.6, 407572.2, 
                                                                                                                                                                                                                                                                  473793.6, 316799.7, 238373.1, 420682.5, 473793.6, 363123.6, 420682.5
                                                                                                                                                                                                                                     ), SF_Plante_senescence = c(0, 0, 0, 4132.8, 0, 0, 20928.6, 20617.8, 
                                                                                                                                                                                                                                                                 35059.5, 51748.2, 19194, 65616.6, 20617.8, 35059.5, 54232.5, 
                                                                                                                                                                                                                                                                 65616.6, 51748.2, 54232.5)), class = c("tbl_df", "tbl", "data.frame"
                                                                                                                                                                                                                                                                 ), row.names = c(NA, -18L))

With the code below, I want to draw a dotted line, but I want to get smooth curves instead of polylines (no polyline segments).And I can't add legend successfully either.

Could anyone please help save my problem? Thank you in advance!

ggplot(df, aes(x = Date_obs)) + 
  stat_summary(aes(y = SF_Plante_Totale,group=1), fun =mean, colour="white",shape=21,size=4,fill="steelblue",geom="point",group=1)+
  stat_summary(aes(y = SF_Plante_Totale,group=1), fun =mean,colour="steelblue", geom="smooth", group=1)+
  stat_summary(aes(y = SF_Plante_Verte,group=1), fun =mean, colour="white",shape=21,size=4,fill="tomato",geom="point",group=2)+
  stat_summary(aes(y = SF_Plante_Verte,group=1), fun =mean,colour="tomato", geom="smooth", group=1)+
  theme(axis.text.x = element_text(angle = 45, hjust = 1))

Answer 1

There are a few issues here.

1. You don't get a legend because you specify the color manually to each layer outside of aes(). {ggplot2} won't automatically make a legend for things specified outside of aes().
2. You can't access the different groups as a single variable to provide in aes() because your data is currently in 'wide' format where you have multiple columns containing the same type of data and the column names are simple metadata distinguishing those measurements. The solution is to convert to 'long' format. For this, I use tidyr::pivot_longer().
3. To get your desired colors you can just use scale_color_manual().
4. If you want to fit a smoothed curve rather than just a point-to-point line, you can use loess smoothing and simply adjust the span parameter to control how smooth or bumpy it is.
5. You can just change the linetype to get a dotted/dashed line. See here for more info on available options to control linetype.
6. If you want to separately visualize data from different Pos_heliaphen groups, it will help to add another aesthetic to distinguish them. For example you could use shape to distinguish the points and linetype to distinguish the smoothed lines.
7. I used interaction() to create all the combinations of the grouping variables.

library(tidyverse)

df %>% 
  select(1, 4:6) %>% 
  pivot_longer(starts_with("SF")) %>% 
  ggplot(aes(Date_obs, value, color = name, group = interaction(name, Pos_heliaphen))) +
  geom_point(stat = "summary", size = 4, aes(shape = Pos_heliaphen)) +
  geom_smooth(method = "loess", se = F, span = 5, aes(linetype = Pos_heliaphen)) +
  scale_color_manual(values = c("steelblue", "tomato")) +
  theme(axis.text.x = element_text(angle = 45, hjust = 1))

^{Created on 2022-04-07 by the reprex package (v2.0.1)}