more professional scatterplot in R - r

I want to produce the scatterplots between the first variable of a dataset and all others, e.g. from iris the Sepal.Length with all others. I have created the following:
data <- iris[,c(-5)]
par(mfrow = c(2, 2))
for (i in seq(ncol(data))[-1]) {
plot(
data[, 1],
data[, i],
xlab = colnames(data)[i],
ylab = "Y"
)
lines(lowess(data[,1],data[,i]),col="red")
}
which results in:
Is there any way to make it looks more professional and not so simple??

ggplot2 is great for this type of thing. There are a bunch of themes that can be used to quickly create high quality plots. It also gives you a lot of flexibilty to customize your plot by changing individual elements.
In addition to being able to make the plots pretty, it is very effective at creating the plots in the first place. Here is somewhere to start :
library(tidyverse)
#your example data
data <- iris[, c(-5)]
#pivot_longer rearranges the data in to a long form, which makes it easier to plot
data_def <- pivot_longer(data, -Sepal.Length)
#the data to be plotted
ggplot(data_def, aes(x = Sepal.Length, y = value)) +
#adding the scatter plot (each value is a point)
geom_point() +
#adding a LOESS smoothed line (the default method of smoothing), without the standard error
geom_smooth(se = FALSE, color = "red", size = 0.5) +
#Splits into the three plots based on the measurements and moves the titles underneath the x-axis
facet_wrap( ~ name, scales = "free_y", strip.position = "bottom") +
#Changes the overall look of the plot
theme_classic() +
#Removes elements of the former title (now x-axis) so that there is no surrounding box
theme(strip.background = element_blank(),
strip.placement = "outside") +
#Manually change the axis labels
labs(x = NULL, y = "Y")
I also use ggpubr which is based on ggplot2

Related

How to turn my legend horizontal as opposed to vertical with ggplot2?

I am struggling to understand why legend.horizontal is not rotating my legend axis so it isn't displaying vertically? Any help would be massively appreciated.
library(phyloseq)
library(ggplot2)
##phylum level
ps_tmp <- get_top_taxa(physeq_obj = ps.phyl, n = 10, relative = TRUE, discard_other = FALSE, other_label = "Other")
ps_tmp <- name_taxa(ps_tmp, label = "Unkown", species = T, other_label = "Other")
phyl <- fantaxtic_bar(ps_tmp, color_by = "phylum", label_by = "phylum",facet_by = "TREATMENT", other_label = "Other", order_alg = "as.is")
phyl + theme(legend.direction = "horizontal", legend.position = "bottom", )
Legends for discrete values don't have a formal direction per se and are positioned however ggplot2 decides it can best fit with your data. This is why things like legend.direction won't work here. I don't have the phyloseq package or access to your particular data, so I'll show you how this works and how you can mess with the legend using a reproducible example dataset.
library(ggplot2)
set.seed(8675309)
df <- data.frame(x=LETTERS[1:8], y=sample(1:100, 8))
p <- ggplot(df, aes(x, y, fill=x)) + geom_col()
p
By default, ggplot is putting our legend to the right and organizes it vertically as one column. Here's what happens when we move the legend to the bottom:
p + theme(legend.position="bottom")
Now ggplot thinks it's best to put that legend into 4 columns, 2 rows each. As u/Tech Commodities mentioned, you can use the guides() functions to specify how the legend looks. In this case, we will specify to have 2 columns instead of 4. We only need to supply the number of columns (or rows), and ggplot figures out the rest.
p + theme(legend.position="bottom") +
guides(fill=guide_legend(ncol=2))
So, to get a "horizontally-arranged" legend, you just need to specify that there should be only one row:
p + theme(legend.position="bottom") +
guides(fill=guide_legend(nrow=1))

How to plot histograms of raw data on the margins of a plot of interpolated data

I would like to show in the same plot interpolated data and a histogram of the raw data of each predictor. I have seen in other threads like this one, people explain how to do marginal histograms of the same data shown in a scatter plot, in this case, the histogram is however based on other data (the raw data).
Suppose we see how price is related to carat and table in the diamonds dataset:
library(ggplot2)
p = ggplot(diamonds, aes(x = carat, y = table, color = price)) + geom_point()
We can add a marginal frequency plot e.g. with ggMarginal
library(ggExtra)
ggMarginal(p)
How do we add something similar to a tile plot of predicted diamond prices?
library(mgcv)
model = gam(price ~ s(table, carat), data = diamonds)
newdat = expand.grid(seq(55,75, 5), c(1:4))
names(newdat) = c("table", "carat")
newdat$predicted_price = predict(model, newdat)
ggplot(newdat,aes(x = carat, y = table, fill = predicted_price)) +
geom_tile()
Ideally, the histograms go even beyond the margins of the tileplot, as these data points also influence the predictions. I would, however, be already very happy to know how to plot a histogram for the range that is shown in the tileplot. (Maybe the values that are outside the range could just be added to the extreme values in different color.)
PS. I managed to more or less align histograms to the margins of the sides of a tile plot, using the method of the accepted answer in the linked thread, but only if I removed all kind of labels. It would be particularly good to keep the color legend, if possible.
EDIT:
eipi10 provided an excellent solution. I tried to modify it slightly to add the sample size in numbers and to graphically show values outside the plotted range since they also affect the interpolated values.
I intended to include them in a different color in the histograms at the side. I hereby attempted to count them towards the lower and upper end of the plotted range. I also attempted to plot the sample size in numbers somewhere on the plot. However, I failed with both.
This was my attempt to graphically illustrate the sample size beyond the plotted area:
plot_data = diamonds
plot_data <- transform(plot_data, carat_range = ifelse(carat < 1 | carat > 4, "outside", "within"))
plot_data <- within(plot_data, carat[carat < 1] <- 1)
plot_data <- within(plot_data, carat[carat > 4] <- 4)
plot_data$carat_range = as.factor(plot_data$carat_range)
p2 = ggplot(plot_data, aes(carat, fill = carat_range)) +
geom_histogram() +
thm +
coord_cartesian(xlim=xrng)
I tried to add the sample size in numbers with geom_text. I tried fitting it in the far right panel but it was difficult (/impossible for me) to adjust. I tried to put it on the main graph (which would anyway probably not be the best solution), but it didn’t work either (it removed the histogram and legend, on the right side and it did not plot all geom_texts). I also tried to add a third row of plots and writing it there. My attempt:
n_table_above = nrow(subset(diamonds, table > 75))
n_table_below = nrow(subset(diamonds, table < 55))
n_table_within = nrow(subset(diamonds, table >= 55 & table <= 75))
text_p = ggplot()+
geom_text(aes(x = 0.9, y = 2, label = paste0("N(>75) = ", n_table_above)))+
geom_text(aes(x = 1, y = 2, label = paste0("N = ", n_table_within)))+
geom_text(aes(x = 1.1, y = 2, label = paste0("N(<55) = ", n_table_below)))+
thm
library(egg)
pobj = ggarrange(p2, ggplot(), p1, p3,
ncol=2, widths=c(4,1), heights=c(1,4))
grid.arrange(pobj, leg, text_p, ggplot(), widths=c(6,1), heights =c(6,1))
I would be very happy to receive help on either or both tasks (adding sample size as text & adding values outside plotted range in a different color).
Based on your comment, maybe the best approach is to roll your own layout. Below is an example. We create the marginal plots as separate ggplot objects and lay them out with the main plot. We also extract the legend and put it outside the marginal plots.
Set-up
library(ggplot2)
library(cowplot)
# Function to extract legend
#https://github.com/hadley/ggplot2/wiki/Share-a-legend-between-two-ggplot2-graphs
g_legend<-function(a.gplot){
tmp <- ggplot_gtable(ggplot_build(a.gplot))
leg <- which(sapply(tmp$grobs, function(x) x$name) == "guide-box")
legend <- tmp$grobs[[leg]]
return(legend) }
thm = list(theme_void(),
guides(fill=FALSE),
theme(plot.margin=unit(rep(0,4), "lines")))
xrng = c(0.6,4.4)
yrng = c(53,77)
Plots
p1 = ggplot(newdat, aes(x = carat, y = table, fill = predicted_price)) +
geom_tile() +
theme_classic() +
coord_cartesian(xlim=xrng, ylim=yrng)
leg = g_legend(p1)
p1 = p1 + thm[-1]
p2 = ggplot(diamonds, aes(carat)) +
geom_line(stat="density") +
thm +
coord_cartesian(xlim=xrng)
p3 = ggplot(diamonds, aes(table)) +
geom_line(stat="density") +
thm +
coord_flip(xlim=yrng)
plot_grid(
plot_grid(plotlist=list(p2, ggplot(), p1, p3), ncol=2,
rel_widths=c(4,1), rel_heights=c(1,4), align="hv", scale=1.1),
leg, rel_widths=c(5,1))
UPDATE: Regarding your comment about the space between the plots: This is an Achilles heel of plot_grid and I don't know if there's a way to fix it. Another option is ggarrange from the experimental egg package, which doesn't add so much space between plots. Also, you need to save the output of ggarrange first and then lay out the saved object with the legend. If you run ggarrange inside grid.arrange you get two overlapping copies of the plot:
# devtools::install_github('baptiste/egg')
library(egg)
pobj = ggarrange(p2, ggplot(), p1, p3,
ncol=2, widths=c(4,1), heights=c(1,4))
grid.arrange(pobj, leg, widths=c(6,1))

Line up columns of bar graph with points of line plot with ggplot

Is there any way to line up the points of a line plot with the bars of a bar graph using ggplot when they have the same x-axis? Here is the sample data I'm trying to do it with.
library(ggplot2)
library(gridExtra)
data=data.frame(x=rep(1:27, each=5), y = rep(1:5, times = 27))
yes <- ggplot(data, aes(x = x, y = y))
yes <- yes + geom_point() + geom_line()
other_data = data.frame(x = 1:27, y = 50:76 )
no <- ggplot(other_data, aes(x=x, y=y))
no <- no + geom_bar(stat = "identity")
grid.arrange(no, yes)
Here is the output:
The first point of the line plot is to the left of the first bar, and the last point of the line plot is to the right of the last bar.
Thank you for your time.
Extending #Stibu's post a little: To align the plots, use gtable (Or see answers to your earlier question)
library(ggplot2)
library(gtable)
data=data.frame(x=rep(1:27, each=5), y = rep(1:5, times = 27))
yes <- ggplot(data, aes(x = x, y = y))
yes <- yes + geom_point() + geom_line() +
scale_x_continuous(limits = c(0,28), expand = c(0,0))
other_data = data.frame(x = 1:27, y = 50:76 )
no <- ggplot(other_data, aes(x=x, y=y))
no <- no + geom_bar(stat = "identity") +
scale_x_continuous(limits = c(0,28), expand = c(0,0))
gYes = ggplotGrob(yes) # get the ggplot grobs
gNo = ggplotGrob(no)
plot(rbind(gNo, gYes, size = "first")) # Arrange and plot the grobs
Edit To change heights of plots:
g = rbind(gNo, gYes, size = "first") # Combine the plots
panels <- g$layout$t[grepl("panel", g$layout$name)] # Get the positions for plot panels
g$heights[panels] <- unit(c(0.7, 0.3), "null") # Replace heights with your relative heights
plot(g)
I can think of (at least) two ways to align the x-axes in the two plots:
The two axis do not align because in the bar plot, the geoms cover the x-axis from 0.5 to 27.5, while in the other plot, the data only ranges from 1 to 27. The reason is that the bars have a width and the points don't. You can force the axex to align by explicitly specifying an x-axis range. Using the definitions from your plot, this can be achieved by
yes <- yes + scale_x_continuous(limits=c(0,28))
no <- no + scale_x_continuous(limits=c(0,28))
grid.arrange(no, yes)
limits sets the range of the x-axis. Note, though, that the alginment is still not quite perfect. The y-axis labels take up a little more space in the upper plot, because the numbers have two digits. The plot looks as follows:
The other solution is a bit more complicated but it has the advantage that the x-axis is drawn only once and that ggplot makes sure that the alignment is perfect. It makes use of faceting and the trick described in this answer. First, the data must be combined into a single data frame by
all <- rbind(data.frame(other_data,type="other"),data.frame(data,type="data"))
and then the plot can be created as follows:
ggplot(all,aes(x=x,y=y)) + facet_grid(type~.,scales = "free_y") +
geom_bar(data=subset(all,type=="other"),stat="identity") +
geom_point(data=subset(all,type=="data")) +
geom_line(data=subset(all,type=="data"))
The trick is to let the facets be constructed by the variable type which was used before to label the two data sets. But then each geom only gets the subset of the data that should be drawn with that specific geom. In facet_grid, I also used scales = "free_y" because the two y-axes should be independent. This plot looks as follows:
You can change the labels of the facets by giving other names when you define the data frame all. If you want to remove them alltogether, then add the following to your plot:
+ theme(strip.background = element_blank(), strip.text = element_blank())

Plotting a bivariate to multiple factors in R

First of all, I'm still a beginner. I'm trying to interpret and draw a stack bar plot with R. I already took a look at a number of answers but some were not specific to my case and others I simply didn't understand:
https://stats.stackexchange.com/questions/31597/graphing-a-probability-curve-for-a-logit-model-with-multiple-predictors
https://stats.stackexchange.com/questions/47020/plotting-logistic-regression-interaction-categorical-in-r
Plot the results of a multivariate logistic regression model in R
I've got a dataset dvl that has five columns, Variant, Region, Time, Person and PrecededByPrep. I'd like to make a multivariate comparison of Variant to the other four predictors. Every column can have one of two possible values:
Variant: elk or ieder.
Region = VL or NL.
Time: time or no time
Person: person or no person
PrecededByPrep: 1 or 0
Here's the logistic regression
From the answers I gathered that the library ggplot2 might be the best drawing library to go with. I've read its documentation but for the life of me I can't figure out how to plot this: how can I get a comparison of Variant with the other three factors?
It took me a while, but I made something similar in Photoshop to what I'd like (fictional values!).
Dark gray/light gray: possible values of Variant
y-axis: frequency
x-axis: every column, subdivided into its possible values
I know to make individual bar plots, both stacked and grouped, but basically I do not know how to have stacked, grouped bar plots. ggplot2 can be used, but if it can be done without I'd prefer that.
I think this can be seen as a sample dataset, though I'm not entirely sure. I am a beginner with R and I read about creating a sample set.
t <- data.frame(Variant = sample(c("iedere","elke"),size = 50, replace = TRUE),
Region = sample(c("VL","NL"),size = 50, replace = TRUE),
PrecededByPrep = sample(c("1","0"),size = 50, replace = TRUE),
Person = sample(c("person","no person"),size = 50, replace = TRUE),
Time = sample(c("time","no time"),size = 50, replace = TRUE))
I'd like to have the plot to be aesthetically pleasing as well. What I had in mind:
Plot colours (i.e. for the bars): col=c("paleturquoise3", "palegreen3")
A bold font for the axis labels font.lab=2 but not for the value labels (e.g. ´regionin bold, butVLandNL` not in bold)
#404040 as a colour for the font, axis and lines
Labels for the axes: x: factors, y: frequency
Here is one possibility which starts with the 'un-tabulated' data frame, melt it, plot it with geom_bar in ggplot2 (which does the counting per group), separate the plot by variable by using facet_wrap.
Create toy data:
set.seed(123)
df <- data.frame(Variant = sample(c("iedere", "elke"), size = 50, replace = TRUE),
Region = sample(c("VL", "NL"), size = 50, replace = TRUE),
PrecededByPrep = sample(c("1", "0"), size = 50, replace = TRUE),
Person = sample(c("person", "no person"), size = 50, replace = TRUE),
Time = sample(c("time", "no time"), size = 50, replace = TRUE))
Reshape data:
library(reshape2)
df2 <- melt(df, id.vars = "Variant")
Plot:
library(ggplot2)
ggplot(data = df2, aes(factor(value), fill = Variant)) +
geom_bar() +
facet_wrap(~variable, nrow = 1, scales = "free_x") +
scale_fill_grey(start = 0.5) +
theme_bw()
There are lots of opportunities to customize the plot, such as setting order of factor levels, rotating axis labels, wrapping facet labels on two lines (e.g. for the longer variable name "PrecededByPrep"), or changing spacing between facets.
Customization (following updates in question and comments by OP)
# labeller function used in facet_grid to wrap "PrecededByPrep" on two lines
# see http://www.cookbook-r.com/Graphs/Facets_%28ggplot2%29/#modifying-facet-label-text
my_lab <- function(var, value){
value <- as.character(value)
if (var == "variable") {
ifelse(value == "PrecededByPrep", "Preceded\nByPrep", value)
}
}
ggplot(data = df2, aes(factor(value), fill = Variant)) +
geom_bar() +
facet_grid(~variable, scales = "free_x", labeller = my_lab) +
scale_fill_manual(values = c("paleturquoise3", "palegreen3")) + # manual fill colors
theme_bw() +
theme(axis.text = element_text(face = "bold"), # axis tick labels bold
axis.text.x = element_text(angle = 45, hjust = 1), # rotate x axis labels
line = element_line(colour = "gray25"), # line colour gray25 = #404040
strip.text = element_text(face = "bold")) + # facet labels bold
xlab("factors") + # set axis labels
ylab("frequency")
Add counts to each bar (edit following comments from OP).
The basic principles to calculate the y coordinates can be found in this Q&A. Here I use dplyr to calculate counts per bar (i.e. label in geom_text) and their y coordinates, but this could of course be done in base R, plyr or data.table.
# calculate counts (i.e. labels for geom_text) and their y positions.
library(dplyr)
df3 <- df2 %>%
group_by(variable, value, Variant) %>%
summarise(n = n()) %>%
mutate(y = cumsum(n) - (0.5 * n))
# plot
ggplot(data = df2, aes(x = factor(value), fill = Variant)) +
geom_bar() +
geom_text(data = df3, aes(y = y, label = n)) +
facet_grid(~variable, scales = "free_x", labeller = my_lab) +
scale_fill_manual(values = c("paleturquoise3", "palegreen3")) + # manual fill colors
theme_bw() +
theme(axis.text = element_text(face = "bold"), # axis tick labels bold
axis.text.x = element_text(angle = 45, hjust = 1), # rotate x axis labels
line = element_line(colour = "gray25"), # line colour gray25 = #404040
strip.text = element_text(face = "bold")) + # facet labels bold
xlab("factors") + # set axis labels
ylab("frequency")
Here is my proposition for a solution with function barplot of base R :
1. calculate the counts
l_count_df<-lapply(colnames(t)[-1],function(nomcol){table(t$Variant,t[,nomcol])})
count_df<-l_count_df[[1]]
for (i in 2:length(l_count_df)){
count_df<-cbind(count_df,l_count_df[[i]])
}
2. draw the barplot without axis names, saving the bar coordinates
par(las=1,col.axis="#404040",mar=c(5,4.5,4,2),mgp=c(3.5,1,0))
bp<-barplot(count_df,width=1.2,space=rep(c(1,0.3),4),col=c("paleturquoise3", "palegreen3"),border="#404040", axisname=F, ylab="Frequency",
legend=row.names(count_df),ylim=c(0,max(colSums(count_df))*1.2))
3. label the bars
mtext(side=1,line=0.8,at=bp,text=colnames(count_df))
mtext(side=1,line=2,at=(bp[seq(1,8,by=2)]+bp[seq(2,8,by=2)])/2,text=colnames(t)[-1],font=2)
4. add values inside the bars
for(i in 1:ncol(count_df)){
val_elke<-count_df[1,i]
val_iedere<-count_df[2,i]
text(bp[i],val_elke/2,val_elke)
text(bp[i],val_elke+val_iedere/2,val_iedere)
}
Here is what I get (with my random data) :
I'm basically answering a different question. I suppose this can be seen as perversity on my part, but I really dislike barplots of pretty much any sort. They have always seemed to create wasted space because the present informationed numerical values are less useful that an appropriately constructed table. The vcd package offers an extended mosaicplot function that seems to me to be more accurately called a "multivariate barplot that any of the ones I have seen so far. It does require that you first construct a contingency table for which the xtabs function seems a perfect fit.
install.packages)"vcd")
library(vcd)
help(package=vcd,mosaic)
col=c("paleturquoise3", "palegreen3")
vcd::mosaic(xtabs(~Variant+Region + PrecededByPrep + Time, data=ttt)
,highlighting="Variant", highlighting_fill=col)
That was the 5 way plot and this is the 5-way plot:
png(); vcd::mosaic( xtabs(
~Variant+Region + PrecededByPrep + Person + Time,
data=ttt)
,highlighting="Variant", highlighting_fill=col); dev.off()

Omitting a Missing x-axis Value in ggplot2 (Convert range to categorical variable)

I am using ggplot to generate a chart that summarises a race made up from several laps. There are 24 participants in the race,numbered 1-12, 14-25; I am plotting out a summary measure for each participant using ggplot, but ggplot assumes I want the number range 1-25, rather than categories 1-12, 14-25.
What's the fix for this? Here's the code I am using (the data is sourced from a Google spreadsheet).
sskey='0AmbQbL4Lrd61dHlibmxYa2JyT05Na2pGVUxLWVJYRWc'
library("ggplot2")
require(RCurl)
gsqAPI = function(key,query,gid){ return( read.csv( paste( sep="", 'http://spreadsheets.google.com/tq?', 'tqx=out:csv', '&tq=', curlEscape(query), '&key=', key, '&gid=', curlEscape(gid) ) ) ) }
sin2011racestatsX=gsqAPI(sskey,'select A,B,G',gid='13')
sin2011proximity=gsqAPI(sskey,'select A,B,C',gid='12')
h=sin2011proximity
k=sin2011racestatsX
l=subset(h,lap==1)
ggplot() +
geom_step(aes(x=h$car, y=h$pos, group=h$car)) +
scale_x_discrete(limits =c('VET','WEB','HAM','BUT','ALO','MAS','SCH','ROS','SEN','PET','BAR','MAL','','SUT','RES','KOB','PER','BUE','ALG','KOV','TRU','RIC','LIU','GLO','AMB'))+
xlab(NULL) + opts(title="F1 2011 Korea \nRace Summary Chart", axis.text.x=theme_text(angle=-90, hjust=0)) +
geom_point(aes(x=l$car, y=l$pos, pch=3, size=2)) +
geom_point(aes(x=k$driverNum, y=k$classification,size=2), label='Final') +
geom_point(aes(x=k$driverNum, y=k$grid, col='red')) +
ylab("Position")+
scale_y_discrete(breaks=1:24,limits=1:24)+ opts(legend.position = "none")
Expanding on my cryptic comment, try this:
#Convert these to factors with the appropriate labels
# Note that I removed the ''
h$car <- factor(h$car,labels = c('VET','WEB','HAM','BUT','ALO','MAS','SCH','ROS','SEN','PET','BAR','MAL',
'SUT','RES','KOB','PER','BUE','ALG','KOV','TRU','RIC','LIU','GLO','AMB'))
k$driverNum <- factor(k$driverNum,labels = c('VET','WEB','HAM','BUT','ALO','MAS','SCH','ROS','SEN','PET','BAR','MAL',
'SUT','RES','KOB','PER','BUE','ALG','KOV','TRU','RIC','LIU','GLO','AMB'))
l=subset(h,lap==1)
ggplot() +
geom_step(aes(x=h$car, y=h$pos, group=h$car)) +
geom_point(aes(x=l$car, y=l$pos, pch=3, size=2)) +
geom_point(aes(x=k$driverNum, y=k$classification,size=2), label='Final') +
geom_point(aes(x=k$driverNum, y=k$grid, col='red')) +
ylab("Position") +
scale_y_discrete(breaks=1:24,limits=1:24) + opts(legend.position = "none") +
opts(title="F1 2011 Korea \nRace Summary Chart", axis.text.x=theme_text(angle=-90, hjust=0)) + xlab(NULL)
Calling scale_x_discrete is no longer necessary. And stylistically, I prefer putting opts and xlab stuff at the end.
Edit
A few notes in response to your comment. Many of your difficulties can be eased by a more streamlined use of ggplot. Your data is in an awkward format:
#Summarise so we can use geom_linerange rather than geom_step
d1 <- ddply(h,.(car),summarise,ymin = min(pos),ymax = max(pos))
#R has a special value for missing data; use it!
k$classification[k$classification == 'null'] <- NA
k$classification <- as.integer(k$classification)
#The other two data sets should be merged and converted to long format
d2 <- merge(l,k,by.x = "car",by.y = "driverNum")
colnames(d2)[3:5] <- c('End of Lap 1','Final Position','Grid Position')
d2 <- melt(d2,id.vars = 1:2)
#Now the plotting call is much shorter
ggplot() +
geom_linerange(data = d1,aes(x= car, ymin = ymin,ymax = ymax)) +
geom_point(data = d2,aes(x= car, y= value,shape = variable),size = 2) +
opts(title="F1 2011 Korea \nRace Summary Chart", axis.text.x=theme_text(angle=-90, hjust=0)) +
labs(x = NULL, y = "Position", shape = "")
A few notes. You were setting aesthetics to fixed values (size = 2) which should be done outside of aes(). aes() is for mapping variables (i.e. columns) to aesthetics (color, shape, size, etc.). This allows ggplot to intelligently create the legend for you.
Merging the second two data sets and then melting it creates a grouping variable for ggplot to use in the legend. I used the shape aesthetic since a few values overlap; using color may make that hard to spot. In general, ggplot will resist mixing aesthetics into a single legend. If you want to use shape, color and size you'll get three legends.
I prefer setting labels using labs, since you can do them all in one spot. Note that setting the aesthetic label to "" removes the legend title.

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