Python - Matplotlib - Axis Labels

Question

I'm trying to plot four figure labels with two decimal places - e.g '1475.88' onto my X-Axis. As you can see the label has been shorted by Matplotlib to the scientific format 1.478e3.

How do I display the full figure, and at a defined spacing.

Code below:

with plt.style.context('seaborn-whitegrid'):

    # Plot the SVP data
    plt.figure(figsize=(8, 8))
    plt.plot(speed_x_clean, depth_y_clean)
    plt.plot(smoothed_speed, smoothed_depth)
    plt.scatter(float(speed_extrapolated), float(depth_extrapolated),marker='X', color='#ff007f')

    # Add a legend, labels and titla
    plt.gca().invert_yaxis()
    plt.legend(('Raw SVP', 'Smoothed SVP'), loc='best')
    plt.title('SVP - ROV '+ '['+ time_now + ']')
    plt.xlabel('Sound Velocity [m/s]')
    plt.ylabel('Depth [m]')

    # plt.grid(color='grey', linestyle='--', linewidth=0.25, grid_animated=True)
    ax = plt.axes()
    plt.gca().xaxis.set_major_locator(plt.AutoLocator())
    plt.xticks(rotation=0)

    plt.show()

score 1 · Accepted Answer · answered Mar 21 '20 at 17:14

Labels with two Decimal Places

Using a ticker FuncFormatter any user defined format can be achieved.

@ticker.FuncFormatter
def major_formatter(val, pos):
    return "%.2f" % val

Labels at a Defined Spacing

With set_xticks and set_yticks the number of labels can be set at a defined spacing.

Self-Contained Example

A completely self-contained example could look like this (simple sine wave):

import matplotlib.pyplot as plt
import numpy as np
import matplotlib.ticker as ticker


@ticker.FuncFormatter
def major_formatter(val, pos):
    return "%.2f" % val


def graph():
    x = np.arange(0.0, 1501, 50)
    y = np.sin(2 * np.pi * x / 1500)

    fig, ax = plt.subplots()
    ax.plot(x, y)

    ax.xaxis.set_major_formatter(major_formatter)
    ax.yaxis.set_major_formatter(major_formatter)

    x_ticks = np.arange(0, 1501, 500)
    y_ticks = np.arange(-1.0, +1.01, 0.5)

    ax.set_xticks(x_ticks)
    ax.set_yticks(y_ticks)

    ax.grid(which='both')

    plt.show()


if __name__ == '__main__':
    graph()

Output

Here the output of the example program: it has four figure labels with two decimal places on the x-axis:

Python - Matplotlib - Axis Labels

1 Answers1