R help - Jul 2023 - How to plot both lines and points by group on ggplot2

Hello,
I have a dataframe with measurements stratified by the concentration
of a certain substance. I would like to plot the points of the
measures and connect the points within each series of concentrations.
When I launch ggplot2 I get the error
```
geom_path: Each group consists of only one observation. Do you need to
adjust the
group aesthetic?
```
and no lines are drawn.
Where am I going wrong?
Thank you
Luigi

```
df = data.frame(Conc = c(rep(1, 3), rep(2, 3), rep(5, 3)),
                Time = rep(1:3, 3),
                Value = c(0.91, 0.67, 0.71, 0.91, 0.65, 0.74, 0.95, 0.67, 0.67))
df$Time <- as.factor(df$Time)
levels(df$Time) = c(1, 4, 24)
df$Conc <- as.factor(df$Conc)
levels(df$Conc) = c(1, 2, 5)
library(ggplot2)
ggplot(df, aes(x=Time, y=Value, colour=Conc)) +
  geom_point(size=6) +
  geom_line(aes(x=Time, y=Value, colour=Conc)) +
  scale_colour_manual(values = c("darkslategray3",
"darkslategray4",
                                 "deepskyblue4")) +
  ggtitle("Working example") +
  xlab(expression(bold("Time (h)"))) +
  ylab(expression(bold("Concentration (mM)")))
```
-- 
Best regards,
Luigi

Can your post a few lines of your data frame (e.g. via
dput(head(...))) to make it clearer. I found this statement confusing:
"... measurements stratified by the concentration
of a certain substance. I would like to plot the points of the
measures and connect the points within each series of concentrations."

This might or might not be the source of your problems, but I think
showing us (enough of) your data would help clarify things. I don't
use ggplot, but someone who does might have a better chance of
pinpointing the problem if you provide such data.

Cheers,
Bert

On Sat, Jul 1, 2023 at 11:21?AM Luigi Marongiu <marongiu.luigi at
gmail.com> wrote:
>
> Hello,
> I have a dataframe with measurements stratified by the concentration
> of a certain substance. I would like to plot the points of the
> measures and connect the points within each series of concentrations.
> When I launch ggplot2 I get the error
> ```
> geom_path: Each group consists of only one observation. Do you need to
> adjust the
> group aesthetic?
> ```
> and no lines are drawn.
> Where am I going wrong?
> Thank you
> Luigi
>
> ```
> df = data.frame(Conc = c(rep(1, 3), rep(2, 3), rep(5, 3)),
>                 Time = rep(1:3, 3),
>                 Value = c(0.91, 0.67, 0.71, 0.91, 0.65, 0.74, 0.95, 0.67,
0.67))
> df$Time <- as.factor(df$Time)
> levels(df$Time) = c(1, 4, 24)
> df$Conc <- as.factor(df$Conc)
> levels(df$Conc) = c(1, 2, 5)
> library(ggplot2)
> ggplot(df, aes(x=Time, y=Value, colour=Conc)) +
>   geom_point(size=6) +
>   geom_line(aes(x=Time, y=Value, colour=Conc)) +
>   scale_colour_manual(values = c("darkslategray3",
"darkslategray4",
>                                  "deepskyblue4")) +
>   ggtitle("Working example") +
>   xlab(expression(bold("Time (h)"))) +
>   ylab(expression(bold("Concentration (mM)")))
> ```
> --
> Best regards,
> Luigi
>
> ______________________________________________
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> and provide commented, minimal, self-contained, reproducible code.

[Whoops, forgot that default reply-to is to the sender.]


On 01/07/2023 19:20, Luigi Marongiu wrote:
> Hello,
> I have a dataframe with measurements stratified by the concentration
> of a certain substance. I would like to plot the points of the
> measures and connect the points within each series of concentrations.
> When I launch ggplot2 I get the error
> ```
> geom_path: Each group consists of only one observation. Do you need to
> adjust the
> group aesthetic?
> ```
> and no lines are drawn.
> Where am I going wrong?
> Thank you
> Luigi
>
> ```
> df = data.frame(Conc = c(rep(1, 3), rep(2, 3), rep(5, 3)),
> Time = rep(1:3, 3),
> Value = c(0.91, 0.67, 0.71, 0.91, 0.65, 0.74, 0.95, 0.67, 0.67))
> df$Time <- as.factor(df$Time)
> levels(df$Time) = c(1, 4, 24)
> df$Conc <- as.factor(df$Conc)
> levels(df$Conc) = c(1, 2, 5)
> library(ggplot2)
> ggplot(df, aes(x=Time, y=Value, colour=Conc)) +
> geom_point(size=6) +
> geom_line(aes(x=Time, y=Value, colour=Conc)) +
> scale_colour_manual(values = c("darkslategray3",
"darkslategray4",
> "deepskyblue4")) +
> ggtitle("Working example") +
> xlab(expression(bold("Time (h)"))) +
> ylab(expression(bold("Concentration (mM)")))
> ```
If I understand what you want then I think all you need is to add "group 
= Conc".? That's what that message is telling you.

df = data.frame(Conc = c(rep(1, 3), rep(2, 3), rep(5, 3)),
 ??????????????? Time = rep(1:3, 3),
 ??????????????? Value = c(0.91, 0.67, 0.71, 0.91, 0.65, 0.74, 0.95, 
0.67, 0.67))
df$Time <- as.factor(df$Time)
levels(df$Time) = c(1, 4, 24)
df$Conc <- as.factor(df$Conc)
levels(df$Conc) = c(1, 2, 5)
library(ggplot2)
ggplot(df, aes(x=Time, y=Value, colour=Conc, group = Conc)) +
 ? geom_point(size=6) +
 ? geom_line(aes(x=Time, y=Value, colour=Conc)) +
 ? scale_colour_manual(values = c("darkslategray3",
"darkslategray4",
 ???????????????????????????????? "deepskyblue4")) +
 ? ggtitle("Working example") +
 ? xlab(expression(bold("Time (h)"))) +
 ? ylab(expression(bold("Concentration (mM)")))

Very? best,


Chris

-- 
Chris Evans (he/him)
Visiting Professor, UDLA, Quito, Ecuador & Honorary Professor, University of
Roehampton, London, UK.
Work web site: https://www.psyctc.org/psyctc/
CORE site: http://www.coresystemtrust.org.uk/
Personal site: https://www.psyctc.org/pelerinage2016/
Emeetings (Thursdays): https://www.psyctc.org/psyctc/booking-meetings-with-me/
(Beware: French time, generally an hour ahead of UK)
<https://ombook.psyctc.org/book>

?s 19:20 de 01/07/2023, Luigi Marongiu escreveu:
> Hello,
> I have a dataframe with measurements stratified by the concentration
> of a certain substance. I would like to plot the points of the
> measures and connect the points within each series of concentrations.
> When I launch ggplot2 I get the error
> ```
> geom_path: Each group consists of only one observation. Do you need to
> adjust the
> group aesthetic?
> ```
> and no lines are drawn.
> Where am I going wrong?
> Thank you
> Luigi
> 
> ```
> df = data.frame(Conc = c(rep(1, 3), rep(2, 3), rep(5, 3)),
>                  Time = rep(1:3, 3),
>                  Value = c(0.91, 0.67, 0.71, 0.91, 0.65, 0.74, 0.95, 0.67,
0.67))
> df$Time <- as.factor(df$Time)
> levels(df$Time) = c(1, 4, 24)
> df$Conc <- as.factor(df$Conc)
> levels(df$Conc) = c(1, 2, 5)
> library(ggplot2)
> ggplot(df, aes(x=Time, y=Value, colour=Conc)) +
>    geom_point(size=6) +
>    geom_line(aes(x=Time, y=Value, colour=Conc)) +
>    scale_colour_manual(values = c("darkslategray3",
"darkslategray4",
>                                   "deepskyblue4")) +
>    ggtitle("Working example") +
>    xlab(expression(bold("Time (h)"))) +
>    ylab(expression(bold("Concentration (mM)")))
> ```
Hello,

Here are two solutions. I have removed the redundant aes() from 
geom_line in both plots.

1. If you do not coerce Time to factor, the x axis will be continuous.
    The plot will be as expected but you wi have to include a 
scale_x_continuous to have the wanted labels.



df = data.frame(Conc = c(rep(1, 3), rep(2, 3), rep(5, 3)),
                 Time = rep(1:3, 3),
                 Value = c(0.91, 0.67, 0.71, 0.91, 0.65, 0.74, 0.95, 
0.67, 0.67))

library(ggplot2)

df$Conc <- factor(df$Conc, levels = c(1, 2, 5))

ggplot(df, aes(x=Time, y=Value, colour=Conc)) +
   geom_point(size=6) +
   geom_line() +
   scale_colour_manual(values = c("darkslategray3",
"darkslategray4",
"deepskyblue4")) +
   scale_x_continuous(breaks = 1:3, labels = c(1, 2, 24)) +
   ggtitle("Working example") +
   xlab(expression(bold("Time (h)"))) +
   ylab(expression(bold("Concentration (mM)")))




2. Time is coerced to factor. Then, tell geom_line the data is grouped 
by Conc. This is probably the solution you should use.



df$Time <- factor(df$Time, labels = c(1, 4, 24))

ggplot(df, aes(x=Time, y=Value, colour=Conc)) +
   geom_point(size=6) +
   geom_line(aes(group = Conc)) +
   scale_colour_manual(values = c("darkslategray3",
"darkslategray4",
"deepskyblue4")) +
   ggtitle("Working example") +
   xlab(expression(bold("Time (h)"))) +
   ylab(expression(bold("Concentration (mM)")))



Hope this helps,

Rui Barradas