Been set this question for an assignment - but i've never used R before - any help is appreciated.
Many thanks.
Question:
Produce a scatter plot to compare CO2 emissions from Brazil and Argentina between 1950 and 2019....
I can get it for Brazil but cannot figure out how to add Argentina.
I think i have to do something with geom_point and filter?
df%>%
filter(Country=="Brazil", Year<=2019 & Year>=1950) %>%
ggplot(aes(x = Year, y = CO2_annual_tonnes)) +
geom_point(na.rm =TRUE, shape=20, size=2, colour="green") +
labs(x = "Year", y = "CO2Emmissions (tonnes)")
The answer depends on what you're looking to do, but generally adding another dimension to a scatter plot where you already have clear x and y dimensions is done by applying an aesthetic (color, shape, etc) or via faceting.
In both approaches, you actually don't want to filter the data. You use either aesthetics or faceting to "filter" in a way and map the data appropriately based on the country column in the dataset. If your dataset contains more countries than Argentina and Brazil, you will want to filter to only include those, so:
your_filtered_df <- your_df %>%
dplyr::filter(Country %in% c("Argentina", "Brazil"))
Faceting
Faceting is another way of saying you want to split up your one plot into two separate plots (one for Argentina, one for Brazil). Each plot will have the same aesthetics (look the same), but will have the appropriate "filtered" dataset.
In your case, you can try:
your_filtered_df %>%
ggplot(aes(x = Year, y = CO2_annual_tonnes)) +
geom_point(na.rm =TRUE, shape=20, size=2, colour="green") +
facet_wrap(~Country)
Aesthetics
Here, you have a lot of options. The idea is that you tell ggplot2 to map the appearance of individual points in the point geom to the value specified in your_filtered_df$Country. You do this by placing one of the aesthetic arguments for geom_point() inside of aes(). If you use shape=, for example it might look like this:
your_filtered_df %>%
ggplot(aes(x = Year, y = CO2_annual_tonnes)) +
geom_point(aes(shape=Country), na.rm =TRUE, size=2, colour="green")
This should show a plot that has a legend created to and two different shapes for the points that correspond to the country name. It's very important to remember that when you put an aesthetic like shape or color or size inside of aes(), you must not also have it outside. So, this will behave correctly:
geom_point(aes(colour=Country), ...)
But this will not:
geom_point(aes(colour=Country), colour="green", ...)
When one aesthetic is outside, it overrides the one in aes(). The second one will still show all points as green.
Don't Do this... but it works
OP posted a comment that indicated some additional hints from the professor, which was:
We were given the hint in the question "you can embed piped filter
functions within geom_point objects"
I believe they are referring to a final... very bad way of generating the points. This method would require you to have two geom_point() objects, and send each one a different filtered dataset. You can do this by accessing the data= argument within each geom_point() object. There are many problems with this approach, including the lack of a legend being generated, but if you simply must do it this way... here it is:
# painful to write this. it goes against all good practices with ggplot
your_filtered_df %>%
ggplot(aes(x = Year, y = CO2_annual_tonnes)) +
geom_point(data=your_filtered_df %>% dplyr::filter(Country=="Argentina"),
color="green", shape=20) +
geom_point(data=your_filtered_df %>% dplyr::filter(Country=="Brazil"),
color="red", shape=20)
You should probably see why this is not a good convention. Think about what you would do for representing 50 different countries... the above codes or methods would work, but with this method, you would have 50 individual geom_point() objects in your plot... ugh. Don't make a typo!
Related
So I'm self-teaching myself R right now using this online resource: "https://r4ds.had.co.nz/data-visualisation.html#facets"
This particular section is going over the use of facet_wrap and facet_grid. It's clear to me that facet_grid is primarily used when wanting to visualize a plot along two additional dimensions, rather than just one. What I don't understand is why you can use facet_grid(.~variable) or facet_grid(variable~.) to basically achieve the same result as facet_wrap. Putting a "." in place of a variable results in just not faceting along the row or column dimension, or in other words showing 1 additional variable just as facet_wrap would do.
If anyone can shed some light on this, thank you!
If you use facet_grid, the facets will always be in one row/column. They will never wrap to make a rectangle. But really if you just have one variable with few levels, it doesn't much matter.
You can also see that facet_grid(.~variable) and facet_grid(variable~.) will put the facet labels in different places (row headings vs column headings)
mg <- ggplot(mtcars, aes(x = mpg, y = wt)) + geom_point()
mg + facet_grid(vs~ .) + labs(title="facet_grid(vs~ .)"),
mg + facet_grid(.~ vs) + labs(title="facet_grid(.~ vs)")
So in the most simple of cases, there's nothing that different between them. The main reason to use facet_grid is to have a single, common axis for all facets so you can easily scan across all panels to make a direct comparison of data.
Actually, the same result is not produced all the time...
The number of facets which appear across the graphs pane is fixed with facet_grid (always the number of unique values in the variable) where as facet_wrap, like its name suggests, wraps the facets around the graphics pane. In this way the functions only result in the same graph when the number of facets produced is small.
Both facet_grid and facet_wrap take their arguments in the form row~columns, and nowdays we don't need to use the dot with facet_grid.
In order to compare their differences let's add a new variable with 8 unqiue values to the mtcars data set:
library(tidyverse)
mtcars$example <- rep(1:8, length.out = 32)
ggplot()+
geom_point(data = mtcars, aes(x = mpg, y = wt))+
facet_grid(~example, labeller = label_both)
Which results in a cluttered plot:
Compared to:
ggplot()+
geom_point(data = mtcars, aes(x = mpg, y = wt))+
facet_wrap(~example, labeller = label_both)
Which results in:
I have used the following code to generate a plot with ggplot:
I want the legend to show the runs 1-8 and only the volumes 12.5 and 25 why doesn't it show it?
And is it possible to show all the points in the plot even though there is an overlap? Because right now the plot only shows 4 of 8 points due to overlap.
OP. You've already been given a part of your answer. Here's a solution given your additional comment and some explanation.
For reference, you were looking to:
Change a continuous variable to a discrete/discontinuous one and have that reflected in the legend.
Show runs 1-8 labeled in the legend
Disconnect lines based on some criteria in your dataset.
First, I'm representing your data here again in a way that is reproducible (and takes away the extra characters so you can follow along directly with all the code):
library(ggplot2)
mydata <- data.frame(
`Run`=c(1:8),
"Time"=c(834, 834, 584, 584, 1184, 1184, 938, 938),
`Area`=c(55.308, 55.308, 79.847, 79.847, 81.236, 81.236, 96.842, 96.842),
`Volume`=c(12.5, 12.5, 12.5, 12.5, 25.0, 25.0, 25.0, 25.0)
)
Changing to a Discrete Variable
If you check the variable type for each column (type str(mydata)), you'll see that mydata$Run is an int and the rest of the columns are num. Each column is understood to be a number, which is treated as if it were a continuous variable. When it comes time to plot the data, ggplot2 understands this to mean that since it is reasonable that values can exist between these (they are continuous), any representation in the form of a legend should be able to show that. For this reason, you get a continuous color scale instead of a discrete one.
To force ggplot2 to give you a discrete scale, you must make your data discrete and indicate it is a factor. You can either set your variable as a factor before plotting (ex: mydata$Run <- as.factor(mydata$Run), or use code inline, referring to aes(size = factor(Run),... instead of just aes(size = Run,....
Using reference to factor(Run) inline in your ggplot calls has the effect of changing the name of the variable to be "factor(Run)" in your legend, so you will have to also add that to the labs() object call. In the end, the plot code looks like this:
ggplot(data = mydata, aes(x=Area, y=Time)) +
geom_point(aes(color =as.factor(Volume), size = Run)) +
geom_line() +
labs(
x = "Area", y = "Time",
# This has to be changed now
color='Volume'
) +
theme_bw()
Note in the above code I am also not referring to mydata$Run, but just Run. It is greatly preferable that you refer to just the name of the column when using ggplot2. It works either way, but much better in practice.
Disconnect Lines
The reason your lines are connected throughout the data is because there's no information given to the geom_line() object other than the aesthetics of x= and y=. If you want to have separate lines, much like having separate colors or shapes of points, you need to supply an aesthetic to use as a basis for that. Since the two lines are different based on the variable Volume in your dataset, you want to use that... but keep the same color for both. For this, we use the group= aesthetic. It tells ggplot2 we want to draw a line for each piece of data that is grouped by that aesthetic.
ggplot(data = mydata, aes(x=Area, y=Time)) +
geom_point(aes(color =as.factor(Volume), size = Run)) +
geom_line(aes(group=as.factor(Volume))) +
labs(
x = "Area", y = "Time", color='Volume'
) +
theme_bw()
Show Runs 1-8 Labeled in Legend
Here I'm reading a bit into what you exactly wanted to do in terms of "showing runs 1-8" in the legend. This could mean one of two things, and I'll assume you want both and show you how to do both.
Listing and showing sizes 1-8 in the legend.
To set the values you see in the scale (legend) for size, you can refer to the various scale_ functions for all types of aesthetics. In this case, recall that since mydata$Run is an int, it is treated as a continuous scale. ggplot2 doesn't know how to draw a continuous scale for size, so the legend itself shows discrete sizes of points. This means we don't need to change Run to a factor, but what we do need is to indicate specifically we want to show in the legend all breaks in the sequence from 1 to 8. You can do this using scale_size_continuous(breaks=...).
ggplot(data = mydata, aes(x=Area, y=Time)) +
geom_point(aes(color =as.factor(Volume), size = Run)) +
geom_line(aes(group=as.factor(Volume))) +
labs(
x = "Area", y = "Time", color='Volume'
) +
scale_size_continuous(breaks=c(1:8)) +
theme_bw()
Showing all of your runs as points.
The note about showing all runs might also mean you want to literally see each run represented as a discrete point in your plot. For this... well, they already are! ggplot2 is plotting each of your points from your data into the chart. Since some points share the same values of x= and y=, you are getting overplotting - the points are drawn over top of one another.
If you want to visually see each point represented here, one option could be to use geom_jitter() instead of geom_point(). It's not really great here, because it will look like your data has different x and y values, but it is an option if this is what you want to do. Note in the code below I'm also changing the shape of the point to be a hollow circle for better clarity, where the color= is the line around each point (here it's black), and the fill= aesthetic is instead used for Volume. You should get the idea though.
set.seed(1234) # using the same randomization seed ensures you have the same jitter
ggplot(data = mydata, aes(x=Area, y=Time)) +
geom_jitter(aes(fill =as.factor(Volume), size = Run), shape=21, color='black') +
geom_line(aes(group=as.factor(Volume))) +
labs(
x = "Area", y = "Time", fill='Volume'
) +
scale_size_continuous(breaks=c(1:8)) +
theme_bw()
I have recently been playing around with various plot types using fictitious data to get my head around how I could display various pieces of information. One plot type that is gaining popularity is the so called individual differences dot plot which shows the change in each subjects score pre-post. The plot is fairly easy to produce, but my issue is that when I go to change the labels using either the labs or xlab ylab functions in ggplot, the plot itself becomes messed up. Below I have attached the fictitious data, the code used and the results.
Data
df<- data.frame(Participant<- c(rep(1:10,2)), Score<- c(rnorm(20,100,5)), Session<- c(1,1,1,1,1,1,1,1,1,1, 2,2,2,2,2,2,2,2,2,2))
colnames(df) <- c("Participant", "Score", "Session")
Code for plot
p<- ggplot(df, aes(x=df$Session, y=df$Score, colour=df$Participant))+ geom_point()+
geom_line(group=df$Participant)+
theme_classic()
Plot
Individual difference plot
My dilemma is that anytime I try to change the label names, the plot messes up as per below.
Problem
p + xlab("Session") + ylab("Score")
Plot after relabelling
The same thing happens if I try the labs function i.e, p + labs(x= "Session", y= "Score"). You can see that the labels themselves do actually change, but for some reason this messes up the actual plot. Does any have any ideas as to what could be going wrong here?
The issue appears to be the grouping is undone when the label functions are called. Instead, issue the grouping as an aesthetic mapping:
library(dplyr); library(ggplot)
df %>% mutate(across(c(Session,Participant),factor)) -> df
p <- ggplot(df, aes(x=Session, y=Score, colour=Participant))+ geom_point()+
geom_line(aes(group=Participant))+
theme_classic()
p + xlab("Session") + ylab("Score")
I suspect this is probably a bug.
I'm plotting a sort of chloropleth of up to three selectable species abundances across a research area. This toy code behaves as expected and does almost what I want:
library(dplyr)
library(ggplot2)
square <- expand.grid(X=0:10, Y=0:10)
sq2 <- square[rep(row.names(square), 2),] %>%
arrange(X,Y) %>%
mutate(SPEC = rep(c('red','blue'),len=n())) %>%
mutate(POP = ifelse(SPEC %in% 'red', X, Y)) %>%
group_by(X,Y) %>%
mutate(CLR = rgb(X/10,0,Y/10)) %>% ungroup()
ggplot(sq2, aes(x=X, y=Y, fill=CLR)) + geom_tile() +
scale_fill_identity("Species", guide="legend",
labels=c('red','blue'), breaks=c('#FF0000','#0000FF'))
Producing this:
A modified version properly plots the real map, appropriately mixing the RGBs to show the species proportions per map unit. But given that mixing, the real data does not necessarily include the specific values listed in breaks, in which case no entry appears in the legend for that species. If you change the last line of the example to
labels=c('red','blue','green'), breaks=c('#FF0000','#0000FF','#00FF00'))
you get the same legend as shown, with only 'red' and 'blue' displayed, as there is no green in it. Searching the data for each max(Species) and assigning those to the legend is possible but won't make good legend keys for species that only occur in low proportions. What's needed is for the legend to display the idea of the entities present, not their attested presences -- three colors in the legend even if only one species is detected.
I'd think that scale_fill_manual() or the override.aes argument might help me here but I haven't been able to make any combination work.
Edit: Episode IV -- A New Dead End
(Thanks #r2evans for fixing my omission of packages.)
I thought I might be able to trick the legend by mutating a further column into the df in the processing pipe called spCLR to represent the color ('#FF0000', e.g.) that codes each entry's species (redundant info, but fine). Now the plotting call in my real version goes:
df %>% [everything] %>%
ggplot(aes(x = X, y = Y, height = WIDTH, width = WIDTH, fill = CLR)) +
geom_tile() +
scale_fill_identity("Species", guide="legend",
labels=spCODE, breaks=spCLR)
But this gives the error: Error in check_breaks_labels(breaks, labels) : object 'spCLR' not found. That seems weird since spCLR is indeed in the pipe-modified df, and of all the values supplied to the ggplot functions spCODE is the only one present in the original df -- so if there's some kind of scope problem I don't get it. [Re-edit -- I see that neither labels nor breaks wants to look at df$anything. Anyway.]
I assume (rightly?) there's some way to make this one work [?], but it still wouldn't make the legend show 'red', 'blue' and 'green' in my toy example -- which is what my original question is really about -- because there is still no actual green-data present in that. So to reiterate, isn't there any way to force a ggplot2 legend to show the things you want to talk about, rather than just the ones that are present in the data?
I have belatedly discovered that my question is a near-duplicate of this. The accepted answer there (from #joran) doesn't work for this but the second answer (from #Axeman) does. So the way for me to go here is that the last line should be
labels=c('red','blue','green'), limits=c('#FF0000','#0000FF','#00FF00'))
calling limits() instead of breaks(), and now my example and my real version work as desired.
I have to say I spent a lot of time digging around in the ggplot2 reference without ever gaining a suspicion that limits() was the correct alternative to breaks() -- which is explicitly mentioned in that ref page while limits() does not appear. The ?limits() page is quite uninformative, and I can't find anything that lays out the distinctions between the two: when this rather than that.
I assume from the heatmap use case that you have no other need for colour mapping in the chart. In this case, a possible workaround is to leave the fill scale alone, & create an invisible geom layer with colour aesthetic mapping to generate the desired legend instead:
ggplot(sq2, aes(x=X, y=Y)) +
geom_tile(aes(fill = CLR)) + # move fill mapping here so new point layer doesn't inherit it
scale_fill_identity() + # scale_*_identity has guide set to FALSE by default
# add invisible layer with colour (not fill) mapping, within x/y coordinates within
# same range as geom_tile layer above
geom_point(data = . %>%
slice(1:3) %>%
# optional: list colours in the desired label order
mutate(col = forcats::fct_inorder(c("red", "blue", "green"))),
aes(colour = col),
alpha = 0) +
# add colour scale with alpha set to 1 (overriding alpha = 0 above),
# also make the shape square & larger to mimic the default legend keys
# associated with fill scale
scale_color_manual(name = "Species",
values = c("red" = '#FF0000', "blue" = '#0000FF', "green" = '#00FF00'),
guide = guide_legend(override.aes = list(alpha = 1, shape = 15, size = 5)))
I'm currently trying to get my head around the differences between stat_* and geom_* in ggplot2. (Please note this is more of an interest/understanding based question than a specific problem I am trying solve).
Introduction
My current understanding is that is that the stat_* functions apply a transformation to your data and that the result is then passed onto the geom_* to be displayed.
Most simple example being the identity transformation which simply passes your data untransformed onto the geom.
ggplot(data = iris) +
stat_identity(aes(x = Sepal.Length, y = Sepal.Width) , geom= "point")
More practical use-cases appear to be when you want to use some transformation and supply the results to a non-default geom, for example if you wanted to plot an error bar of the 1st and 3rd quartile you could do something like:
ggplot(data = iris) +
stat_boxplot(aes(x=Species, y = Sepal.Length, ymax = ..upper.., ymin = ..lower..), geom = "errorbar")
Question 1
So how / when are these transformations applied to the dataset and how does data pass through them exactly?
As an example, say I wanted to take the stat_boxplot transformation and plot the point of the 3rd quartile how would I do this ?
My intuition would be something like :
ggplot(data = iris) +
stat_boxplot(aes(x=Species, y = ..upper..) , geom = "point")
or
ggplot(data = iris) +
stat_boxplot(aes(x=Species, y = Sepal.Length) , geom = "point")
however both error with
Error: geom_point requires the following missing aesthetics: y
My guess is as part of the stat_boxplot transformation it consumes the y aesthetic and produces a dataset not containing any y variable however this leads onto ....
Question 2
Where can I find out which variables are consumed as part of the stat_* transformation and what variables they output? Maybe i'm looking in the wrong places but the documentation does not seem clear to me at all...
Interesting questions...
As background info, you can read this chapter of R for Data Science, focusing on the grammar of graphics. I'm sure Hadley Wickham's book on ggplot2 is even a better source, but I don't have that one.
The main steps for building a graph with one layer and no facet are:
Apply aesthetics mapping on input data (in simple cases, this is a selection and renaming on columns)
Apply scale transformation (if any) on each data column
Compute stat on each data group (i.e. per Species in this case)
Apply aesthetics mapping on stat data, detected with ..<name>.. or stat(name)
Apply position adjustment
Build graphical objects
Apply coordinate transformations
As you guessed, the behaviour at step 3 is similar to dplyr::transmute(): it consumes all aesthetics columns and outputs a data frame having as columns all freshly computed stats and all columns that are constant within the group. The stat output may also have a different number of rows from its input. Thus indeed in your example the y column isn't passed to the geom.
To do this, we'd like to specify different mappings at step 1 (before stat) and at step 4 (before geom). I thought something like this would work:
# This does not work:
ggplot(data = iris) +
geom_point(
aes(x=Species, y=stat(upper)),
stat=stat_boxplot(aes(x=Species, y=Sepal.Length)) )
... but it doesn't (stat must be a string or a Stat object, but stat_boxplot actually returns a Layer object, like geom_point does).
NB: stat(upper) is an equivalent, more recent, notation to your ..upper..
I might be wrong but I don't think there is a way of doing this directly within ggplot. What you can do is extract the stat part of the process above and manage it yourself before entering ggplot():
library(tidyverse)
iris %>%
group_by(Species) %>%
select(y=Sepal.Length) %>%
do(StatBoxplot$compute_group(.)) %>%
ggplot(aes(Species, upper)) + geom_point()
A bit less elegant, I admit...
For your question 2, it's in the doc: see sections Aesthetics and Computed variables of ?stat_boxplot