Dear Bruno,
There are (at least) two errors here:
(1) I think that you misunderstand how interaction.plot(), and more
generally R base graphics, work. interaction.plot() doesn't return a
graphics object, but rather draws on a graphics device as a side effect.
Of course, interaction.plot() is a function and so it must return
something -- it invisibly returns NULL.
(2) I assume that you independently computed Scaphmeans and Scaphse,
although you didn't include the corresponding code in your message. In
any event, the arrows() function generally takes 4 arguments (x0, y0,
x1, y1), specifying the x and y coordinates of the endpoints of the
arrows. It's true that because your "arrows" are intended to be
vertical, you need not specify x1, which defaults to x0, but the other 3
arguments are necessary. See ?arrows for details.
I hope this helps,
John
John Fox, Professor Emeritus
McMaster University
Hamilton, Ontario, Canada
web: https://socialsciences.mcmaster.ca/jfox/
On 2021-06-15 9:02 a.m., Bruno.Salonen wrote:
Hi all,
I'm trying to add error bars to an existing line graph in base R.
The basic line graph comes up just fine, but it does not show my error
bars...
Data frame = readscaphfileNEW
Plot name = SCAPHLINEGRAPHNEW
x axis = TEMP
y axis = SCAPH.BPM
Tracer = Year (SAME AS 'EXPERIMENT)
Scaphmeans = means of SCAPH.BPM
Scaphse = standard error of SCAPH.BPM
Here is the code..
SCAPHLINEGRAPHNEW <- interaction.plot(readscaphfileNEW$TEMP,
readscaphfileNEW$EXPERIMENT, readscaphfileNEW$SCAPH.BPM,
xlab = "Temperature (°C)", ylab = "Scaphognathite Rate (BPM)",
main = "Scaphognathite",
ylim = c(0,300), trace.label = "Year",
type = "b", pch = c(19,17), fixed = TRUE)
arrows(SCAPHLINEGRAPHNEW,Scaphmeans+Scaphse,SCAPHLINEGRAPHNEW,Scaphmeans-Scaphse,code=3,
angle=90, length=0.1)
Why are my error bars not showing? Is the 'arrows' line wrong?
Thanks a million for your help, everybody.
Here is my data set:
readscaphfileNEW
EXPERIMENT TEMP SCAPH.BPM
1 2021 12 82
2 2021 12 58
3 2021 12 78
4 2021 12 59
5 2021 12 80
6 2021 12 100
7 2021 12 61
8 2021 12 103
9 2021 12 61
10 2021 17 100
11 2021 17 70
12 2021 17 83
13 2021 17 73
14 2021 17 143
15 2021 17 103
16 2021 17 73
17 2021 17 158
18 2021 17 95
19 2021 17 80
20 1939 12 158
21 1939 12 148
22 1939 12 152
23 1939 12 148
24 1939 12 160
25 1939 12 168
26 1939 12 152
27 1939 12 150
28 1939 12 187
29 1939 17 300
30 1939 17 302
31 1939 17 291
32 1939 17 240
33 1939 17 253
34 1939 17 207
35 1939 17 184
36 1939 17 224
37 1939 17 242
38 1939 17 236
Bruno
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