Contour Plots in Python
How to make Contour plots in Python with Plotly.
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Basic Contour Plot¶
A 2D contour plot shows the contour lines of a 2D numerical array z, i.e. interpolated lines of isovalues of z.
In [1]:
import plotly.graph_objects as go
fig = go.Figure(data =
go.Contour(
z=[[10, 10.625, 12.5, 15.625, 20],
[5.625, 6.25, 8.125, 11.25, 15.625],
[2.5, 3.125, 5., 8.125, 12.5],
[0.625, 1.25, 3.125, 6.25, 10.625],
[0, 0.625, 2.5, 5.625, 10]]
))
fig.show()
Setting X and Y Coordinates in a Contour Plot¶
In [2]:
import plotly.graph_objects as go
fig = go.Figure(data =
go.Contour(
z=[[10, 10.625, 12.5, 15.625, 20],
[5.625, 6.25, 8.125, 11.25, 15.625],
[2.5, 3.125, 5., 8.125, 12.5],
[0.625, 1.25, 3.125, 6.25, 10.625],
[0, 0.625, 2.5, 5.625, 10]],
x=[-9, -6, -5 , -3, -1], # horizontal axis
y=[0, 1, 4, 5, 7] # vertical axis
))
fig.show()
Colorscale for Contour Plot¶
In [3]:
import plotly.graph_objects as go
fig = go.Figure(data =
go.Contour(
z=[[10, 10.625, 12.5, 15.625, 20],
[5.625, 6.25, 8.125, 11.25, 15.625],
[2.5, 3.125, 5., 8.125, 12.5],
[0.625, 1.25, 3.125, 6.25, 10.625],
[0, 0.625, 2.5, 5.625, 10]],
colorscale='Electric',
))
fig.show()
Customizing Size and Range of a Contour Plot's Contours¶
In [4]:
import plotly.graph_objects as go
fig = go.Figure(data =
go.Contour(
z=[[10, 10.625, 12.5, 15.625, 20],
[5.625, 6.25, 8.125, 11.25, 15.625],
[2.5, 3.125, 5., 8.125, 12.5],
[0.625, 1.25, 3.125, 6.25, 10.625],
[0, 0.625, 2.5, 5.625, 10]],
colorscale='Hot',
contours=dict(
start=0,
end=8,
size=2,
),
))
fig.show()
Customizing Spacing Between X and Y Axis Ticks¶
In [5]:
import plotly.graph_objects as go
fig = go.Figure(data =
go.Contour(
z= [[10, 10.625, 12.5, 15.625, 20],
[5.625, 6.25, 8.125, 11.25, 15.625],
[2.5, 3.125, 5., 8.125, 12.5],
[0.625, 1.25, 3.125, 6.25, 10.625],
[0, 0.625, 2.5, 5.625, 10]],
dx=10,
x0=5,
dy=10,
y0=10,
)
)
fig.show()
Connect the Gaps Between None Values in the Z Matrix¶
In [6]:
import plotly.graph_objs as go
from plotly.subplots import make_subplots
fig = make_subplots(rows=2, cols=2, subplot_titles=('connectgaps = False',
'connectgaps = True'))
z = [[None, None, None, 12, 13, 14, 15, 16],
[None, 1, None, 11, None, None, None, 17],
[None, 2, 6, 7, None, None, None, 18],
[None, 3, None, 8, None, None, None, 19],
[5, 4, 10, 9, None, None, None, 20],
[None, None, None, 27, None, None, None, 21],
[None, None, None, 26, 25, 24, 23, 22]]
fig.add_trace(go.Contour(z=z, showscale=False), 1, 1)
fig.add_trace(go.Contour(z=z, showscale=False, connectgaps=True), 1, 2)
fig.add_trace(go.Heatmap(z=z, showscale=False, zsmooth='best'), 2, 1)
fig.add_trace(go.Heatmap(z=z, showscale=False, connectgaps=True, zsmooth='best'), 2, 2)
fig['layout']['yaxis1'].update(title=dict(text='Contour map'))
fig['layout']['yaxis3'].update(title=dict(text='Heatmap'))
fig.show()
Smoothing the Contour lines¶
In [7]:
import plotly.graph_objects as go
from plotly.subplots import make_subplots
import numpy as np
z = [[2, 4, 7, 12, 13, 14, 15, 16],
[3, 1, 6, 11, 12, 13, 16, 17],
[4, 2, 7, 7, 11, 14, 17, 18],
[5, 3, 8, 8, 13, 15, 18, 19],
[7, 4, 10, 9, 16, 18, 20, 19],
[9, 10, 5, 27, 23, 21, 21, 21],
[11, 14, 17, 26, 25, 24, 23, 22]]
fig = make_subplots(rows=1, cols=2,
subplot_titles=('Without Smoothing', 'With Smoothing'))
fig.add_trace(go.Contour(z=z, line_smoothing=0), 1, 1)
fig.add_trace(go.Contour(z=z, line_smoothing=0.85), 1, 2)
fig.show()
Smooth Contour Coloring¶
In [8]:
import plotly.graph_objects as go
fig = go.Figure(data=
go.Contour(
z=[[10, 10.625, 12.5, 15.625, 20],
[5.625, 6.25, 8.125, 11.25, 15.625],
[2.5, 3.125, 5., 8.125, 12.5],
[0.625, 1.25, 3.125, 6.25, 10.625],
[0, 0.625, 2.5, 5.625, 10]],
# heatmap gradient coloring is applied between each contour level
contours_coloring='heatmap' # can also be 'lines', or 'none'
)
)
fig.show()
Contour Line Labels¶
In [9]:
import plotly.graph_objects as go
fig = go.Figure(data=
go.Contour(
z=[[10, 10.625, 12.5, 15.625, 20],
[5.625, 6.25, 8.125, 11.25, 15.625],
[2.5, 3.125, 5., 8.125, 12.5],
[0.625, 1.25, 3.125, 6.25, 10.625],
[0, 0.625, 2.5, 5.625, 10]],
contours=dict(
coloring ='heatmap',
showlabels = True, # show labels on contours
labelfont = dict( # label font properties
size = 12,
color = 'white',
)
)))
fig.show()
Contour Lines¶
In [10]:
import plotly.graph_objects as go
fig = go.Figure(data=
go.Contour(
z=[[10, 10.625, 12.5, 15.625, 20],
[5.625, 6.25, 8.125, 11.25, 15.625],
[2.5, 3.125, 5., 8.125, 12.5],
[0.625, 1.25, 3.125, 6.25, 10.625],
[0, 0.625, 2.5, 5.625, 10]],
contours_coloring='lines',
line_width=2,
)
)
fig.show()
Custom Contour Plot Colorscale¶
In [11]:
import plotly.graph_objects as go
# Valid color strings are CSS colors, rgb or hex strings
colorscale = [[0, 'gold'], [0.5, 'mediumturquoise'], [1, 'lightsalmon']]
fig = go.Figure(data =
go.Contour(
z=[[10, 10.625, 12.5, 15.625, 20],
[5.625, 6.25, 8.125, 11.25, 15.625],
[2.5, 3.125, 5., 8.125, 12.5],
[0.625, 1.25, 3.125, 6.25, 10.625],
[0, 0.625, 2.5, 5.625, 10]],
colorscale=colorscale)
)
fig.show()
Color Bar Title¶
In [12]:
import plotly.graph_objects as go
fig = go.Figure(data=
go.Contour(
z=[[10, 10.625, 12.5, 15.625, 20],
[5.625, 6.25, 8.125, 11.25, 15.625],
[2.5, 3.125, 5., 8.125, 12.5],
[0.625, 1.25, 3.125, 6.25, 10.625],
[0, 0.625, 2.5, 5.625, 10]],
colorbar=dict(
title=dict(
text='Color bar title', # title here
side='right',
font=dict(
size=14,
family='Arial, sans-serif')
)
),
))
fig.show()
Color Bar Size for Contour Plots¶
In the example below, both the thickness (given here in pixels) and the length (given here as a fraction of the plot height) are set.
In [13]:
import plotly.graph_objects as go
fig = go.Figure(data=
go.Contour(
z=[[10, 10.625, 12.5, 15.625, 20],
[5.625, 6.25, 8.125, 11.25, 15.625],
[2.5, 3.125, 5., 8.125, 12.5],
[0.625, 1.25, 3.125, 6.25, 10.625],
[0, 0.625, 2.5, 5.625, 10]],
colorbar=dict(
thickness=25,
thicknessmode='pixels',
len=0.6,
lenmode='fraction',
outlinewidth=0
)
))
fig.show()
Styling Color Bar Ticks for Contour Plots¶
In [14]:
import plotly.graph_objects as go
fig = go.Figure(data =
go.Contour(
z=[[10, 10.625, 12.5, 15.625, 20],
[5.625, 6.25, 8.125, 11.25, 15.625],
[2.5, 3.125, 5., 8.125, 12.5],
[0.625, 1.25, 3.125, 6.25, 10.625],
[0, 0.625, 2.5, 5.625, 10]],
colorbar=dict(nticks=10, ticks='outside',
ticklen=5, tickwidth=1,
showticklabels=True,
tickangle=0, tickfont_size=12)
))
fig.show()
Reference¶
See https://plotly.com/python/reference/contour/ for more information and chart attribute options!
What About Dash?¶
Dash is an open-source framework for building analytical applications, with no Javascript required, and it is tightly integrated with the Plotly graphing library.
Learn about how to install Dash at https://dash.plot.ly/installation.
Everywhere in this page that you see fig.show(), you can display the same figure in a Dash application by passing it to the figure argument of the Graph component from the built-in dash_core_components package like this:
import plotly.graph_objects as go # or plotly.express as px
fig = go.Figure() # or any Plotly Express function e.g. px.bar(...)
# fig.add_trace( ... )
# fig.update_layout( ... )
from dash import Dash, dcc, html
app = Dash()
app.layout = html.Div([
dcc.Graph(figure=fig)
])
app.run_server(debug=True, use_reloader=False) # Turn off reloader if inside Jupyter
