I am using Plotly+Python. How can I plot a single vector, as represented by an arrow, in 3D?
Annotations (which would have been a hacky workaround) are 2D-only, and Quiver plots are also 2D-only.
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As plotly has no line segments, you can't really do this very well. You could draw a line from one point to another, and do something funny at the end that might look a bit like an arrowhead, but the necessary primitives to do it right don't seem to be there.Mike Wise– Mike Wise2017-04-03 21:03:02 +00:00Commented Apr 3, 2017 at 21:03
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You can also checkout this animation image from 3Blue1Brown. Grant, the creator, has created a beautiful way to do it, but it doesn't utilize Plotly. Link: github.com/3b1b/manimDustin– Dustin2020-08-08 14:46:29 +00:00Commented Aug 8, 2020 at 14:46
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3 Answers
I think you can use a combination of line and cone in 3D. Suppose your line starts from (x, y, z) and ends at (p, q, r), then cone accepts X Y Z and U V W. Now you can set X = p, Y= q, Z=r which is middle point of base of cone. To get cone pointing in same direction as line but less than length of line (say 10%), you can set U = 0.1*(p-x), V = 0.1*(q-y), W = 0.1*(r-z).
1 Comment
qwr
Brilliant solution
From Abdul Saboor's answer this is how (in plotly.js) I made reasonable looking colored arrows:
// example arrow endpoints
const x = [0.5, 1];
const y = [1, 2];
const z = [0, 0.5];
const data = [
{
x: x,
y: y,
z: z,
mode: "lines",
type: "scatter3d",
hoverinfo: "none",
line: {
color: "blue",
width: 3
}
},
{
type: "cone",
x: [x[1]],
y: [y[1]],
z: [z[1]],
u: [0.3*(x[1]-x[0])],
v: [0.3*(y[1]-y[0])],
w: [0.3*(z[1]-z[0])],
anchor: "tip", // make cone tip be at endpoint
hoverinfo: "none",
colorscale: [[0, "blue"], [1, "blue"]], // color all cones blue
showscale: false,
}
];
Plotly.newPlot('myDiv',data);<head>
<!-- Load plotly.js into the DOM -->
<script src='https://cdn.plot.ly/plotly-2.3.1.min.js'></script>
</head>
<body>
<div id='myDiv'><!-- Plotly chart will be drawn inside this DIV --></div>
</body>
1 Comment
Derek O
Very nice! I stumbled on Abdul Saboor's answer some time ago as well, and used his idea as a template to answer the same question, in Plotly Python as opposed to Plotly.js
As Mike Wise mentioned, it is not possible to do it straight forwardly, nevertheless, you can compute your vector and then plot it by drawing the line to the origin:
For example: Plot some points in 3D and draw a vector corresponding to the centroid of those points
import plotly.graph_objs as go
from plotly.offline import plot
#prepare plotting points
#points are: (0,5,5),(5,0,0),(5,10,5),(10,5,5)
points = go.Scatter3d( x = [0,5,5,10],
y = [5,0,10,5],
z = [5,0,5,0],
mode = 'markers',
marker = dict( size = 2,
color = "rgb(227,26,28)")
)
#Compute centroid of all 3 points by taking the mean of each of
#its coordinates (not sure this is the right definition of centroid)
centerX = (0+5+5+10) / float(4)
centerY = (5+0+10+5) / float(4)
centerZ = (5+0+5+0) / float(4)
#Prepare centroid vector
vector = go.Scatter3d( x = [0,centerX],
y = [0,centerY],
z = [0,centerZ],
marker = dict( size = 1,
color = "rgb(84,48,5)"),
line = dict( color = "rgb(84,48,5)",
width = 6)
)
data = [points,vector]
layout = go.Layout(margin = dict( l = 0,
r = 0,
b = 0,
t = 0)
)
fig = go.Figure(data=data,layout=layout)
plot(fig,filename="vector.html",auto_open=False,image='png',image_height=800,image_width=1500)
This will produce:
It will be much better if you open the interactive html file
