Color in stripchart

Dear fellow R users,

I'd like to color individual points in a stripchart. This works well as
long as I have only a single value per y axis category:

df <- data.frame(year = seq(2011, 2018), value = seq(10,80, 10))
df$color <- 'black'
df[df$value<33,]$color <- 'blue'
df[df$value>66,]$color <- 'red'
stripchart(df$value ~ df$year, pch=18, col=df$color, method='stack')

When I use multiple values per y axis category, all points in a specific
y axis category have the same color:

set.seed(20210310)
years <- sample(x=seq(2011, 2018), size = 365*8, replace = TRUE)
values <- sample(x=seq(0,100), size = 365*8, replace = TRUE)
df <- data.frame(year = years, value = values)
df$color <- 'black'
df[df$value<33,]$color <- 'blue'
df[df$value>66,]$color <- 'red'
stripchart(df$value ~ df$year, pch=18, col=df$color, method='stack')

I'd expect to see all points with a value below 33 in blue color, all
points with a value above 66 in red color, and the remaining points in
black color.

I can use a black stripchart plot as basis and plot blue and red points
over the black ones, but I do not get the stacking right:

stripchart(df$value ~ df$year, pch=18, method='stack')
points(df[df$color=='blue',]$value, df[df$color=='blue',]$year-2010,
type='p', pch=18, col='blue')
points(df[df$color=='red',]$value, df[df$color=='red',]$year-2010,
type='p', pch=18, col='red')

Am I somehow misusing the stripchart function?


Best regards,

Robin

Dear Robin and Gerrit,

I am unable to see the difference in the 
plot in the two cases ... 

	df <- data.frame(year = seq(2011, 2018), value = seq(10, 80, 10))
	df$color <- 'black'
	df[df$value<33,]$color <- 'blue'
	df[df$value>66,]$color <- 'red'
	
	file <- "/tmp/robin.png"
	width <- 1000
	height <- 1000
	res <- 150
	png(file=file, width=width, height=height, res=res)
	par(mfrow=c(2,1))
	
	stripchart(df$value ~ df$year, pch=18, col=df$color, method='stack', main="stripchart with color column as col")
	
	stripchart(df$value ~ df$year, pch=18, method='stack', main="stripchart with black basis")
	points(df[df$color=='blue',]$value, df[df$color=='blue',]$year-2010,
	type='p', pch=18, col='blue')
	points(df[df$color=='red',]$value, df[df$color=='red',]$year-2010,
	type='p', pch=18, col='red')
	
	dev.off()

Best,
Rasmus

Dear Robin,

if you study stripchart's code (graphics:::stripchart) carefully
you will find out that the elements of the vector provided to the
col-argument (and the pch-argument as well) are selected by iterating
along the groups (in your case year). I don't seen easy solution for
your problem using stripchart, but you may want to look at the
examples of function beeswarm in package beeswarm.

?Hth? --? Gerrit

---------------------------------------------------------------------
Dr. Gerrit Eichner?????????????????? Mathematical Institute, Room 212
gerrit.eichner at math.uni-giessen.de?? Justus-Liebig-University Giessen
Tel: +49-(0)641-99-32104????????? Arndtstr. 2, 35392 Giessen, Germany
http://www.uni-giessen.de/eichner
---------------------------------------------------------------------

Am 10.03.2021 um 14:08 schrieb Dr. Robin Haunschild:

Dear fellow R users,

I'd like to color individual points in a stripchart. This works well as
long as I have only a single value per y axis category:

df <- data.frame(year = seq(2011, 2018), value = seq(10,80, 10))
df$color <- 'black'
df[df$value<33,]$color <- 'blue'
df[df$value>66,]$color <- 'red'
stripchart(df$value ~ df$year, pch=18, col=df$color, method='stack')

When I use multiple values per y axis category, all points in a specific
y axis category have the same color:

set.seed(20210310)
years <- sample(x=seq(2011, 2018), size = 365*8, replace = TRUE)
values <- sample(x=seq(0,100), size = 365*8, replace = TRUE)
df <- data.frame(year = years, value = values)
df$color <- 'black'
df[df$value<33,]$color <- 'blue'
df[df$value>66,]$color <- 'red'
stripchart(df$value ~ df$year, pch=18, col=df$color, method='stack')

I'd expect to see all points with a value below 33 in blue color, all
points with a value above 66 in red color, and the remaining points in
black color.

I can use a black stripchart plot as basis and plot blue and red points
over the black ones, but I do not get the stacking right:

stripchart(df$value ~ df$year, pch=18, method='stack')
points(df[df$color=='blue',]$value, df[df$color=='blue',]$year-2010,
type='p', pch=18, col='blue')
points(df[df$color=='red',]$value, df[df$color=='red',]$year-2010,
type='p', pch=18, col='red')

Am I somehow misusing the stripchart function?


Best regards,

Robin

Hello there again,

Sorry, I missed that part in the middle 
about set.seed.  As per [1], you need to 
run stripchart again with the add 
argument set to TRUE, and slicing the df 
according to the color, like so

	set.seed(20210310)
	years <- sample(x=seq(2011, 2018), size = 365*8, replace = TRUE)
	values <- sample(x=seq(0,100), size = 365*8, replace = TRUE)
	df <- data.frame(year = years, value = values)
	df$color <- 'black'
	df[df$value<33,]$color <- 'blue'
	df[df$value>66,]$color <- 'red'
	
	stripchart(value ~ year, pch=18, method='stack', data=df)
	for (color in unique(df$color)) {
	  stripchart(value ~ year, pch=18, method='stack', data=df[df$color==color,], col=color, add=TRUE)
	}

Best,
Rasmus

[1] https://stackoverflow.com/questions/32833210/define-color-for-each-datapoint-in-a-stripchart-separately