Missing shapes in legend with scale_shape_manual

I believe the missing shapes are because you had set alpha=0 for the
last geom point. 

I expect there are better ways, but one way to handle it would be to
avoid the filtering, adding columns with med and exercise status,
like the following:

# setup with data provided
Date <- c('2023-10-17', '2023-10-16', '2023-10-15', '2023-10-14',
???????? '2023-10-13', '2023-10-12', '2023-10-11')
Time <- c('08:50', '06:58', '09:17', '09:04', '08:44', '08:55',
'07:55') 
bg <- c(128, 144, 137, 115, 136, 122, 150)
missed_meds <- c(TRUE, FALSE, FALSE, FALSE, FALSE, FALSE, TRUE)
no_exercise <- c(FALSE, FALSE, TRUE, FALSE, TRUE, TRUE, TRUE)

b2 <- data.frame(Date, Time, bg, missed_meds, no_exercise)

b2$Date <- as.Date(b2$Date)
# add "status" columns, could also be defined as factor. 
b2$medStat <- c("missed_meds",NA, NA, NA, NA, NA, "missed_meds")
b2$exercise <- c(NA, NA, "missed_exercise",NA,"missed_exercise",
"missed_exercise", "missed_exercise")

Then your ggplot call would be like this:

ggplot(data = b2, aes(x = Date, y = bg)) +
? geom_line() +
? geom_point(aes(shape = medStat), size = 3)+
? geom_point(aes(shape = exercise),size = 3)+
? scale_y_continuous(name = "Blood glucose (mg/dL)",
???????????????????? breaks = seq(100, 230, by = 20)
? ) +
? geom_hline(yintercept = 130) +
? scale_shape_manual(name = "Conditions",
???????????????????? labels = c("Missed meds",
??????????????????????????????? "Missed exercise"),
???????????????????? values = c(20, 4)
? )


Note that this method then gets very close without the
scale_shape_manual, too. 

Hope that helps. 
Tim

Date: Mon, 30 Oct 2023 20:55:17 +0000
From: Kevin Zembower <kevin at zembower.org>
To: r-help at r-project.org?<r-help at r-project.org>
Subject: [R] Missing shapes in legend with scale_shape_manual
Message-ID:
??????? <0100018b825e8f7f-646d2539-f8b5-4e1a-afc3-5d29f961967f-
000000 at email.amazonses.com>

Content-Type: text/plain; charset="utf-8"

Hello,

I'm trying to plot a graph of blood glucose versus date. I also
record
conditions, such as missing the previous night's medications, and
missing
exercise on the previous day. My data looks like:

b2[68:74,]

# A tibble: 7 ? 5
? Date?????? Time????? bg missed_meds no_exercise
? <date>???? <time> <dbl> <lgl>?????? <lgl>
1 2023-10-17 08:50??? 128 TRUE??????? FALSE
2 2023-10-16 06:58??? 144 FALSE?????? FALSE
3 2023-10-15 09:17??? 137 FALSE?????? TRUE
4 2023-10-14 09:04??? 115 FALSE?????? FALSE
5 2023-10-13 08:44??? 136 FALSE?????? TRUE
6 2023-10-12 08:55??? 122 FALSE?????? TRUE
7 2023-10-11 07:55??? 150 TRUE??????? TRUE

This gets me most of the way to what I want:

ggplot(data = b2, aes(x = Date, y = bg)) +
??? geom_line() +
??? geom_point(data = filter(b2, missed_meds),
?????????????? shape = 20,
?????????????? size = 3) +
??? geom_point(data = filter(b2, no_exercise),
?????????????? shape = 4,
?????????????? size = 3) +
??? geom_point(aes(x = Date, y = bg, shape = missed_meds),
?????????????? alpha = 0) + #Invisible point layer for shape
mapping
??? scale_y_continuous(name = "Blood glucose (mg/dL)",
?????????????????????? breaks = seq(100, 230, by = 20)
?????????????????????? ) +
??? geom_hline(yintercept = 130) +
??? scale_shape_manual(name = "Conditions",
?????????????????????? labels = c("Missed meds",
????????????????????????????????? "Missed exercise"),
?????????????????????? values = c(20, 4),
?????????????????????? ## size = 3
?????????????????????? )

However, the legend just prints an empty square in front of the
labels.
What I want is a filled circle (shape 20) in front of "Missed meds"
and a filled
circle (shape 4) in front of "Missed exercise."

My questions are:
?1. How can I fix my plot to show the shapes in the legend?
?2. Can my overall plotting method be improved? Would you do it
this way?

Thanks so much for your advice and guidance.

-Kevin