Colorbar size that match graph or image is required to get good visualize effect. This can be achieved using any one of following approaches.
Use fraction parameter to match graph
Fraction parameter in colorbar() is used to set the size of colorbar in Python. Using this we can match colorbar size to graph as:
- If vertical colorbar is used, then fraction=0.047 * (height_of_image / width_of_image)
- If horizontal colorbar is used, then fraction=0.047 * (width_of_image / height_of_image)
Approach
- Import module
- Plot a graph
- Set fraction parameter
- Plot colorbar
- Display plot
Example 1:
Here we are importing the required libraries and then plotting the graph, we are calculating the ratio then we are setting the fraction parameter and plotting the colorbar and finally displaying it.
Python3
import matplotlib.pyplot as pltimport numpy as np# Plot an imagea = np.random.random((10, 20))plt.imshow(a, cmap='gray')# Calculate (height_of_image / width_of_image)im_ratio = a.shape[0]/a.shape[1]# Plot vertical colorbarplt.colorbar(fraction=0.047*im_ratio)plt.show() |
Output:
Set Matplotlib colorbar size to match graph
Example 2:
Python3
import matplotlib.pyplot as pltimport numpy as np# Plot an imagea = np.random.random((10, 20))plt.imshow(a, cmap='gray')# Calculate (width_of_image/height_of_image)im_ratio = a.shape[1]/a.shape[0]# Plot horizontal colorbarplt.colorbar(orientation="horizontal", fraction=0.047*im_ratio)plt.show() |
Output:
Set Matplotlib colorbar size to match graph
Using axes_grid1 toolkit to match graph
Axis_grid1 provides a helper function make_axes_locatable() which takes an existing axes instance and creates a divider for it. It provides append_axes() method that creates a new axes on the given side (“top”, “right”, “bottom” and “left”) of the original axes.
Approach:
- Import module
- Plot image
- Divide existing axes instance using make_axes_locatable()
- Create new axes using append_axes()
- Use “top” or “bottom” side for horizontal colorbar
- Use “left” or “right” side for vertical colorbar
- Plot colorbar on created axis
Example 1:
Python3
import matplotlib.pyplot as pltfrom mpl_toolkits.axes_grid1 import make_axes_locatableimport numpy as np# Plot image on axes axax = plt.gca()img = np.random.random((10, 20))im = plt.imshow(img, cmap='gray')# Divide existing axes and create new axes# at bottom side of imagedivider = make_axes_locatable(ax)cax = divider.append_axes("bottom", size="5%", pad=0.25)# Plot horizontal colorbarplt.colorbar(im, orientation="horizontal", cax=cax)plt.show() |
Output:
Set Matplotlib colorbar size to match graph
Example 2:
Python3
import matplotlib.pyplot as pltfrom mpl_toolkits.axes_grid1 import make_axes_locatableimport numpy as np# Plot image on axes axax = plt.gca()img = np.random.random((10, 20))im = plt.imshow(img, cmap='gray')# Divide existing axes and create# new axes at right side of imagedivider = make_axes_locatable(ax)cax = divider.append_axes("right", size="5%", pad=0.15)# Plot vertical colorbarplt.colorbar(im, cax=cax)plt.show() |
Output:
Set Matplotlib colorbar size to match graph
Using add_axes() method to match graph
Giving a colorbar its own axes using add_axes() method, can be an approach to get a colorbar matching given image.
Approach:
- Plot a figure
- Create axes using add_axes() method with position parameters:
- For vertical colorbar on right side of the image:
- left: Left point for colorbar=Right End position of image
- bottom: Bottom point of colorbar= Bottom end position of image
- width: Width of colorbar
- height: Height of colorbar=Height of image
- For horizontal colorbar at bottom of the image:
- left: Left point for colorbar=Left End position of image
- bottom: Bottom point of colorbar= Bottom end position of image
- width: Width of colorbar =Width of image
- height: Height of colorbar
- Plot colorbar on created axes
Example 1 :
Python3
import matplotlib.pyplot as pltimport numpy as np# Plot imagefig = plt.figure()ax = plt.axes()img = np.random.random((10, 20))im = plt.imshow(img, cmap='gray')# Create new axes according to image positioncax = fig.add_axes([ax.get_position().x1+0.01, ax.get_position().y0, 0.02, ax.get_position().height])# Plot vertical colorbarplt.colorbar(im, cax=cax)plt.show() |
Output:
Set Matplotlib colorbar size to match graph
Example 2:
Python3
import matplotlib.pyplot as pltimport numpy as np# Plot an imagefig = plt.figure()ax = plt.axes()img = np.random.random((10, 20))im = plt.imshow(img, cmap='gray')# Create new axes according to image positioncax = fig.add_axes([ax.get_position().x0, ax.get_position().y0-0.08, ax.get_position().width, 0.02])# Plot horizontal colorbar on created axesplt.colorbar(im, orientation="horizontal", cax=cax)plt.show() |
Output:
Set Matplotlib colorbar size to match graph
Prerequisites: Matplotlib
