Is there a way in ggplot to add multiple legends?

Question

I have the dataframe (d):

     d<- structure(list(Total.VolumeD = c(1118.4, 638.4, 1180.8, 1166.4, 
1296, 936, 1324.8, 936, 307.2, 1152, 691.2, 585.6, 648, 979.2, 
374.4, 1358.4, 676.8, 777.6, 1344, 1286.4, 825.6, 849.6, 1056, 
1785.6, 868.8, 1579.2, 283.2, 1132.8, 820.8, 1291.2, 1833.6, 
614.4), Speed_KM = c(27.353, 109.412, 109.412, 78.841, 109.412, 
75.623, 111.021, 114.239, 106.194, 107.803, 112.63, 109.412, 
114.239, 112.63, 90.104, 45.052, 107.803, 109.412, 111.021, 111.021, 
109.412, 94.931, 109.412, 64.36, 43.443, 104.585, 106.194, 106.194, 
104.585, 45.052, 82.059, 102.976), Precipitation = structure(c(1L, 
1L, 1L, 1L, 1L, 2L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L), .Label = c("0", 
"0-50", "50-100", "100-200", ">200"), class = "factor")), row.names = c(NA, 
-32L), class = "data.frame")

I added two geom_paths from the following two datasets:

no_d<- structure(list(q = c(1572.837685, 1310.733335, 1464.593355, 1806.375156, 
1852.930416, 1844.816783, 1723.916843, 1215.776704, 1292.854462
), u = c(55L, 36L, 46L, 107L, 102L, 104L, 109L, 31L, 35L)), row.names = c(NA, 
-9L), class = "data.frame")

and

with_d<- structure(list(q = c(1358.242525, 1334.898171, 1640.129166, 1648.496715, 
1558.353432, 565.2914834, 1472.853017, 1303.752995, 1326.376898
), u = c(51L, 107L, 95L, 99L, 106L, 11L, 64L, 46L, 48L)), row.names = c(NA, 
-9L), class = "data.frame")

I used the following code to plot what I really want. It worked really fine. However, I need to have legend for the precipitation and a another legend for the new two lines (the geom_path lines).

ggplot(d) +
  geom_point(aes( x = Total.VolumeD,y = Speed_KM, width = 0.5,shape=Precipitation, color=Precipitation, 
                  size = Precipitation))+
  scale_colour_manual(values = c("lightgrey", "black", "black", "black", "black"))+
  geom_path(data = no_d, aes(q, u),  size = 1, linetype="solid")+
  geom_path(data = with_d, aes(q, u), size = 1, linetype="dashed")+
  theme(panel.grid.major = element_blank(), panel.grid.minor = element_blank(),
        panel.background = element_blank(),
        panel.border = element_rect(colour = "black", fill=NA, size=1))+
  scale_x_continuous(limits = c(0,2300))+
  scale_y_continuous(limits = c(20,125))+
  labs(shape = "precipitation(mm/h)")

Answer 1

This works,

ggplot(d) +
    geom_point(aes( x = Total.VolumeD,y = Speed_KM, width = 0.5,shape=Precipitation, color=Precipitation, 
                    size = Precipitation))+
    scale_colour_manual(values = c("lightgrey", "black", "black", "black", "black"))+
    # add linetype in aes
    geom_path(data = no_d, aes(q, u, linetype="solid"),  size = 1)+
    geom_path(data = with_d, aes(q, u,linetype="dashed"), size = 1)+
    theme(panel.grid.major = element_blank(), panel.grid.minor = element_blank(),
          panel.background = element_blank(),
          panel.border = element_rect(colour = "black", fill=NA, size=1))+
    scale_x_continuous(limits = c(0,2300))+
    scale_y_continuous(limits = c(20,125))+
    labs(shape = "precipitation(mm/h)") +
    # add this
    scale_linetype_discrete(name = "Y series", labels = c("solid", "dashed"))

UPDATE

ggplot(d) +
    geom_point(aes(Total.VolumeD, Speed_KM, width = 0.5, shape = Precipitation, 
                   color = Precipitation, size = Precipitation))+
    scale_colour_manual(values = c("lightgrey", "black", "black", "black", "black"), guide = "none")+
    geom_path(data = no_d, aes(q, u, linetype = "solid"),  size = 1)+
    geom_path(data = with_d, aes(q, u,linetype = "dashed"), size = 1)+
    theme(panel.grid.major = element_blank(), panel.grid.minor = element_blank(),
          panel.background = element_blank(),
          panel.border = element_rect(colour = "black", fill=NA, size=1))+
    scale_x_continuous(limits = c(0,2300))+
    scale_y_continuous(limits = c(20,125))+
    labs(shape = "precipitation(mm/h)") +
    scale_linetype_discrete(name = "Y series", labels = c("solid", "dashed")) +
    scale_size_discrete(guide = "none")

• In the scale_colour_manual add guide = 'none'
• Add scale_size_discrete(guide = "none")

You are getting legends because you are giving colour and size in aes.
ggplot will return every legend parameter given inside aesthetic.