ggplot2: Different legend symbols for points and lines

Question

already searched all related threads about this but could not find a solution.

Here is my code and the attached plot result:

g <-ggplot(NDVI2, aes(LAI2, NDVI, colour = Legend)) + 
    theme_bw (base_family = "Times") + 
    scale_colour_manual (values = c("purple", "green", "blue", "yellow",  "magenta","orange", "cyan", "red", "black")) + 
    geom_point (size = 3) +
    geom_smooth (aes(group = 1, colour = "Trendline"), method = "loess", size = 1, linetype = 5, se = FALSE) +
    geom_smooth (aes(group = 1, colour = "Regression (log)"),linetype = 1, size=1.2,method = "lm", formula = y~ log(x), se = FALSE) + 
    labs (title = "Correlation of LAI and NDVI")+ 
    theme (legend.title = element_text (size = 15)) 

Which results in this plot:

As you can see, all Legend Icons look the same. What I want is that the points are shown as points and the two lines ("Regression" and "Trendline") are shown as lines.

I tried to use

guides (colour = guide_legend (override.aes = list(size = 1.5)))

but that gives me again all icons in the same way and I can not figure out how to distinguish between them

I´m new to R and this is my first "complex" plot. Try to figure out most with online helps and google but can´t find a solution for this problem. Thank you all for your time and help!

Here a dput of my data:

dput(NDVI2)
structure(list(MeanRED = c(3.240264, 6.97950484, 3.75052276, 
4.62617908, 4.07743944, 4.88961572, 3.15865532, 2.28368236, 3.40793788, 
4.28833416, 4.52529496, 2.45698208, 3.84003364, 4.31006672, 3.29672264, 
4.21926652, 4.64357012, 3.94445908, 3.95942484, 1.22673756, 4.70933136, 
5.33718396, 5.71857348, 5.7014266, 3.85938572, 6.07816804, 2.93602476, 
5.00289296), MeanNIR = c(46.8226195806452, 48.4417953548387, 
47.8913064516129, 43.9416386774194, 44.7524788709677, 52.2142607741935, 
48.6422146774194, 44.6617992580645, 57.7213822580645, 58.5066447096774, 
56.6924350967742, 57.4100250967742, 58.0419292903226, 58.7054423225806, 
58.5283540645161, 54.7658463548387, 58.8950077096774, 58.2421209354839, 
57.8538210645161, 50.209727516129, 59.5780209354839, 60.1662100645161, 
62.1929408387097, 60.3309026451613, 57.859932516129, 63.5678422258065, 
55.2536370967742, 60.1808743548387), NDVI = c(0.870552242769623, 
0.748129155560663, 0.854748647859414, 0.809496111062421, 0.832994214160536, 
0.828746627367857, 0.878046244390978, 0.902709173224405, 0.888500710549276, 
0.863417928083076, 0.852157374806182, 0.917918660181389, 0.875891666709934, 
0.863206160341016, 0.893353221193523, 0.856937918252258, 0.853834622095331, 
0.873141147848366, 0.871890732089488, 0.952300860559358, 0.853491201866442, 
0.837040994913869, 0.831587513918106, 0.827314084928549, 0.874937512911774, 
0.825455384542418, 0.899087753174211, 0.846498808949291), LAI2 = c(1.1, 
1.2, 1.3, 1.4, 2.1, 2.2, 2.3, 2.4, 3.1, 3.2, 3.3, 3.4, 4.1, 4.2, 
4.3, 4.4, 5.1, 5.2, 5.3, 5.4, 6.1, 6.2, 6.3, 6.4, 7.1, 7.2, 7.3, 
7.4), Legend = c("LAI 1", "LAI 1", "LAI 1", "LAI 1", "LAI 2", 
"LAI 2", "LAI 2", "LAI 2", "LAI 3", "LAI 3", "LAI 3", "LAI 3", 
"LAI 4", "LAI 4", "LAI 4", "LAI 4", "LAI 5", "LAI 5", "LAI 5", 
"LAI 5", "LAI 6", "LAI 6", "LAI 6", "LAI 6", "LAI 7", "LAI 7", 
"LAI 7", "LAI 7")), .Names = c("MeanRED", "MeanNIR", "NDVI", 
"LAI2", "Legend"), class = "data.frame", row.names = c("LAI 1-1", 
"LAI 1-2", "LAI 1-3", "LAI 1-4", "LAI 2-1", "LAI 2-2", "LAI 2-3", 
"LAI 2-4", "LAI 3-1", "LAI 3-2", "LAI 3-3", "LAI 3-4", "LAI 4-1", 
"LAI 4-2", "LAI 4-3", "LAI 4-4", "LAI 5-1", "LAI 5-2", "LAI 5-3", 
"LAI 5-4", "LAI 6-1", "LAI 6-2", "LAI 6-3", "LAI 6-4", "LAI 7-1", 
"LAI 7-2", "LAI 7-3", "LAI 7-4"))

Answer 1

override.aes is definitely a good start for customizing the legend. In your case you may remove unwanted shape in the legend by setting them to NA , and set unwanted linetype to blank :

ggplot(data = NDVI2, aes(x = LAI2, y = NDVI, colour = Legend)) + 
  geom_point(size = 3) +
  geom_smooth(aes(group = 1, colour = "Trendline"),
               method = "loess", se = FALSE, linetype = "dashed") +
  geom_smooth(aes(group = 1, colour = "Regression (log)"),
               method = "lm", formula = y ~ log(x), se = FALSE, linetype = "solid") +
  scale_colour_manual(values = c("purple", "green", "blue", "yellow", "magenta","orange", "cyan", "red", "black"),
                       guide = guide_legend(override.aes = list(
                         linetype = c(rep("blank", 7), "solid", "dashed"),
                         shape = c(rep(16, 7), NA, NA))))