Increasing line size in color legend when using both color and size aesthetics?

[Jeff Marcus]

I can't figure out how to increase line thickness in a legend where I am using both color and size aesthetics. Here is sample code:

 df <-data.frame(x.left=1:8, x.right=1:8, y.bot=2:9, y.top=3:10, color.var=c(rep("a", 4), rep("b", 4)), width.var=rep(c("c", "d"),,4))

#> df

#  x.left x.right y.bot y.top color.var width.var

#1      1       1     2     3         a         c

#2      2       2     3     4         a         d

#3      3       3     4     5         a         c

#4      4       4     5     6         a         d

#5      5       5     6     7         b         c

#6      6       6     7     8         b         d

#7      7       7     8     9         b         c

# 8      8       8     9    10         b         d

 gp <- ggplot(df) + geom_segment(aes(x=x.left,xend=x.right, y=y.bot, yend=y.top, color=color.var, size=width.var))

print (gp)

This produces the attached plot thin_legend_lines.png where the width of the lines in the color.var legend is very thin and hard to distinguish in my real use case where I am using 7 colors. 

I tried two things:Increasing legend key size:

(A) Increasing legend key size

require("grid")

gp <- gp + theme(legend.key.size=unit(1,"cm"))

print (gp)

That increased the size of the background in the legend but didn't change the line width. 

(B) Making line size constant.

gp <- ggplot(df) + geom_segment(aes(x=x.left,xend=x.right, y=y.bot, yend=y.top, color=color.var, size=width.var), size=5)

That actually did make the legend lines have size 5 but overrode my size aesthetics setting (i.e., all lines were of size 5).(I expected this but gave it a shot anyways). 

Any ideas on how to preserve the size aesthetic while making the lines in the color legend thicker? Thanks. 

  Jeff

[Dennis Murphy]

Hi:

Is
gp + guides(color = guide_legend(override.aes = list(size = 2)))

along the lines of what you were after?

Dennis

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[Jeff Marcus]

Exactly! Thanks very much. 

 Jeff

[Saurajyoti Kar]

Thanks so much!!

Saurajyoti

[Jason Brannock]

Hello! I know this is a pretty old thread, but I'm running into almost this exact issue and I haven't been able to find any solutions. In my ggplot2 plot, I've got three facets, each with its own color scheme (the default color scheme) rather than a continuation of colors, so each facet has red, blue, and green and each legend is labeled with the proper category (see below). This was accomplished with new_scale_color() after each "data = ~ subset(., filter)" geom_line layer. However, I'm publishing this content in a bookdown and when it's published, those tiny legend lines are almost non-existent. 

I've tried using legend.key and using guides(color = guide_legend(override.aes = list(size = 50)) and neither work. Legend.key made the lines a little bigger, but not enough. If I remove the last new_scale_color(), override.aes does change the lines how I want, but only for the last legend. I need the lines bigger for all three legends. 

Thank you,

Jason

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