Changing legend key from symbol to color block in ggplot2

[Deirdre Griffin]

Hi again,

2 questions...

1) Anyone know how to change legend keys for colour from the default colored circle to a colored block corresponding to the assigned color?

I've been trying to do this with the attached graph because having the circle could be confusing given that I have a circle and triangle designating other treatment factors. I tried a couple of things, including making the circle really huge with guides(colour = override.aes = list(size = 20)  and then trying to keep the legend key box small with theme(legend.key = element.rect(size = 0.5).  But alas that did not work and only caused a horrible disproportioned legend with giant circles...

And while I'm at it...

2) Does anyone know how I can make all of the shapes outlined in black but filled with the two assigned colors? I can't figure out how to do this without either making them all filled blank or changing all the points to be circles instead of having the designated shapes.

Any help would be much appreciated!

Thanks!
Deirdre

Here's my code: 

N2015 %>%
	group_by(Date, Treatment, Biochar, Fertilizer) %>%
	summarise(avgNO3 = mean(NO3_N, na.rm = TRUE),
	seNO3 = (sd(NO3_N, na.rm = TRUE)/sqrt(4))) %>%
	ggplot(aes(x = Treatment, y = avgNO3)) +
	geom_errorbar(aes(ymax = avgNO3 + seNO3, ymin = avgNO3 - seNO3, width = 0.2)) +
	geom_point(aes(shape = Fertilizer, colour = Biochar), size = 6) +
	labs(fill = "Biochar") +
	ylab(bquote('mg'*~NO[3]^`-`~-N~kg^-1 ~ dry ~ soil*'')) +
	scale_shape_discrete(labels = c("Compost", "Mineral")) +
	scale_colour_manual(values = c("grey65", "grey10"), labels = c("No", "Yes")) +
	facet_grid(~ Date) +
	guides(colour = guide_legend(order = 2,
	#override.aes = list(size = 20)
	),
	shape = guide_legend(order = 1)) +
	theme_bw() +
	theme(axis.title.x = element_text(size = 15),
	axis.title.y = element_text(face = "bold", size = 15, vjust = 1),
	axis.text.x = element_blank(),
	axis.text.y = element_text(size = 12),
	legend.title = element_text(size = 15),
	legend.text = element_text(size = 12),
	#legend.key = element_rect(size = 0.5),
	panel.grid.minor = element_blank(), panel.grid.major = element_blank(),
	axis.ticks.x = element_blank(),
	strip.text.x = element_text(size = 15))

[Michael Levy]

Hi Deirdre,

My solutions both involve changing shape elements, the codes for which can be found here.

1. You got close with aes.override… you can use it to change the shape directly.

2. You can do this by mapping your Biochar variable to fill and then setting the color (which is the outline of points) to “black”, but you have to use a filled-point for this, such as shape 21.

Here’s a MWE:

library(ggplot2)
d = data.frame(x = rnorm(10), y = rnorm(10), z = sample(letters[1:2], 10, TRUE))
ggplot(d, aes(x, y, fill = z)) +
    geom_point(shape = 21, color = 'black', size = 5) +
    guides(fill = guide_legend(override.aes = list(shape = 22)))

​

-- 
Michael Levy
c: 304-376-4523

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[Deirdre Griffin]

Thanks, Michael.

Figured out the legend thing. Thanks!

Still having a bit of trouble on the black outline. Managed to the shapes to two filled-point shapes, but for some reason, whenever I map Biochar to fill instead of color, the legend for this is filled black, even though I have  scale_fill_manual(values = c("grey70", "grey10")) in there. 

Please see two versions attached and code below. Any ideas how to fix this?

Thanks!

Deirdre

N2015 %>%
	group_by(Date, Treatment, Biochar, Fertilizer) %>%
	summarise(avgNO3 = mean(NO3_N, na.rm = TRUE),

	seNO3 = (sd(NO3_N, na.rm = TRUE) /sqrt(4))) %>%
	ggplot(aes(x = Treatment, y = avgNO3, fill= Biochar)) +

geom_errorbar(aes(ymax = avgNO3 + seNO3, ymin = avgNO3 - seNO3, width = 0.2)) +

geom_point(aes(shape = Fertilizer), size = 6) +

	labs(fill = "Biochar") +
	ylab(bquote('mg'*~NO[3]^`-`~-N~kg^-1 ~ dry ~ soil*'')) +
	scale_shape_discrete(labels = c("Compost", "Mineral")) +

	scale_shape_manual(values = c(21, 24)) +
	scale_fill_manual(values = c("grey70", "grey10"), labels = c("No", "Yes")) +
	facet_grid(~ Date) +
	guides(fill = guide_legend(order = 2,
	override.aes = list(shape = 15, size = 9)),

	shape = guide_legend(order = 1)) +
	theme_bw() +
	theme(axis.title.x = element_text(size = 15),
	axis.title.y = element_text(face = "bold", size = 15, vjust = 1),
	axis.text.x = element_blank(),
	axis.text.y = element_text(size = 12),
	legend.title = element_text(size = 15),
	legend.text = element_text(size = 12),

legend.key = element_rect(color = "white"),

	panel.grid.minor = element_blank(), panel.grid.major = element_blank(),
	axis.ticks.x = element_blank(),
	strip.text.x = element_text(size = 15))

[Michael Levy]

In that shape-guide I linked to, it looks like point-shapes 15-20 have a fill, but they don’t — they’re always solid black. So change the 15 in this line to a number between 21 and 25 and you should be good:

guides(fill = guide_legend(order = 2, override.aes = list(shape = 15, size = 9)), shape = guide_legend(order = 1))

​

-- 
Michael Levy
c: 304-376-4523