Matplotlib: Making Subplots

Making Subplots

• In real world we often need to compare multiple graphs side by side, for example Temperature Vs. Humidity, Sales Vs. Profit then subplots allow us to create multiple plots in single figure window.

1) The subplot() function

Syntax

plt.subplot(nrows,ncols,index)

Where

nrows: Number of rows in subplot grid

ncols: Number of columns in the subplot grid

index: Position of current plot(counted left to right and top to bottom)

Python program

import matplotlib.pyplot as plt

x=(1,2,3,4,5]

y1=[2,4,6,8,10]

y2=[1,4,9,16,25]

plt.subplot(1,2,1)

plt.plot(x,y1,'r‒‒')

plt.title("plot#1")

plt.subplot(1,2,2)

plt.plot(x,y2,'b‒.')

plt.title("plot #2")

plt.suptitle("Main Plot")

plt.show()

Output

Code explanation: In above code,

1) We have imported the library file Matplotlib.

2) We have with us common x axis co‒ordinates and y1 and y2 arrays for y axis co‒ordinates.

3) plt.subplot(1, 2, 1): Creates a subplot grid with row 1 and two columns and activates first subplot.

4) plt.plot(x, y1, 'r‒‒'): It plots yl Vs x in the first subplot. The 'r‒‒' means red dashed line.

5) plt.title("plot#1"): Sets the title of the first subplot.

6) plt.subplot(1, 2, 2): Activates the second subplot in the same 1*2 grid.

7) plt.plot(x, y2, 'b‒.'): It plots y2 vs x in the second subplot. The 'b‒.' means blue dash (lol reM)eluque lig dot line.

8) plt.title("plot#2"): Sets the title of the second subplot.

9) plt.suptitle("Main Plot"): This adds the title(super title) for entire plot, above both the subplots.

10) Finally using plt.show() the plot with both the subplots is displayed.

2) The subplots() function

• This is more flexible and modern way to create subplots.

syntax

fig, axes = plt.subplots(nrows, ncols)

Where

fig: It is entire figure

axes: It is an array of subplot axes objects.

•  Following is a simple Python program that illustrates how to have subplots using subplots() function.

Python program

import matplotlib.pyplot as plt

x=(1,2,3,4,5]

y1=[2,4,6,8,10]

y2=[1,4,9,16,25]

fig,axes = plt.subplots(1,2)

axes[0].plot(x,y1,color = 'red')

axes[0].set_title("plot#1")

axes[1].plot(x,y2,color = 'blue')

axes[1].set_title("plot#2")

plt.suptitle("Main Plot")

plt.show()

Output

•  In above code we are using axes and it gives direct access to each subplot (object‒oriented style). We can easily modify each plot independently (titles, labels, colors, etc.)

Difference between Plot and Subplot.

Plot

1.It is used to create a single plot in a figure.

2.The simple plt.plot(x,y) function is used.

3.We can modify the title, labels, colors, etc., for a single plot.

4.It is simple and straightforward.

Subplot

1.It is used to create multiple plots within the single figure.

2.In order to arrange multiple plots in rows and columns plt.subplot(rows, cols, index)  function is used.

3.Each subplot can have its own title, labels, and formatting.

4.It is more complex as it involves managing agongwans ( the layout and appearance of multiple plots.