how to make the shape thicker in the scatterplot

[cynthiashuang]

Hi all,

How to make the shape thicker in ggplot? I manually choose shape value = 1,2,3,4. But I cannot find a parameter in ggplot to adjust/tune the thickness of the marker. Is there any straight forward way to do it?

Below is my program.

  p <- ggplot(test, aes(y=y, x=x, 

                               colour=a_b, shape=a_b)) + 

    geom_point(position=position_jitter(width=0.2, height=0.1), na.rm = TRUE) + 

    

    xlab("Baseline X") + ylab("% Y Change from Baseline") + scale_colour_discrete(name  ="A:B") + scale_shape_manual(values=c(1,2,3,4), name ="A:B") +

#theme with white background

theme_bw() +

  

  #eliminates background, gridlines

  theme(

    plot.background = element_blank()

    ,panel.grid.major = element_blank()

    ,panel.grid.minor = element_blank()

  )  

Thanks,

Cynthia

[Phillip Burger]

Hi, Cynthia.  The attachment does not contain any content.  I can download the attachment and open it, but there is not sample plot or other information. If you still have the question and can post the sample plot to provide further, please attach it and I or another member in the group will try to help.

-Phil

[Dennis Murphy]

Hi:

Thankfully, this thread was resurrected so I'll give it a shot. This
should get you close to what you want. Using a simple toy example,

DF <- data.frame(x = rnorm(30), y = rnorm(30),
gp = sample(LETTERS[1:4], 30, replace = TRUE))

library(ggplot2)
library(grid)

p <- ggplot(DF, aes(x, y)) +
geom_point(aes(shape = gp, fill = gp), size = 3.5,
color = "black") +
scale_shape_manual(values = 21:25)

grid.edit("geom_point.points", grep = TRUE, gp = gpar(lwd = 2))


Notes:

1. Shapes 21-25 allow fill color, which explains the choice in
scale_shape_manual().
2. To thicken the line borders, you need to use grid graphics
directly. This is what the last line does, which comes from a
StackOverflow question answered by Sandy Muspratt in August, 2013:
http://stackoverflow.com/questions/17677687/change-thickness-of-a-marker-in-ggplot2
3. You need to fix the point color before you can thicken the shape
borders; clearly, you want the border color to differ from the fill
color unless you want to play with alpha transparency, which is
another option..
4. I know the next question is going to be how to make the border
thickness in the legend the same as that in the graph. I tried without
success. It probably involves some combination of guide_legend() with
the override.aes argument and some appropriate incantation from grid
graphics, but I don't know enough about the latter yet to make it
work. Perhaps someone else can fill the gap.

Dennis

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