Matplotlib: charts

Note: The Python graphics library matplotlib can be used in interactive mode, often using the following command

plt.show()

However, it is often useful to have Python work in batch mode (e.g., as a process on a web server) so that it is useful to save the graphics output to an image file and then save that image file, using the figure and save capability.

Here is the Python code [#1]

import os
import matplotlib as mpl
import matplotlib.pyplot as plt
from PIL import Image
import numpy as np
import matplotlib as mpl
import matplotlib.pyplot as plt
imagePos1 = 0
rlen1 = 1
clen1 = 1
dpi1 = 72
width1 = 640
height1 = 480
figSize1 = (width1 / dpi1, height1/dpi1)
fig1, ax1 = plt.subplots(rlen1,clen1,figsize=figSize1,dpi=dpi1)
dataList1 = [
	0, 42, 43, 47, 65, 43, 7, 0,
	43, 43, 59, 44, 47, 20, 35, 35, 55,
	37, 63, 40, 59, 47, 44, 50, 47, 28,
	45, 29, 9, 29, 30, 62, 21, 53, 45, 23,
	47, 15, 26, 27, 27, 60, 33, 34, 31
	]
binLen1 = 10
fig1 = plt.figure()
plt.hist(
	dataList1,
	bins=[0,10,20,30,40,50,60,70],
	facecolor="green",
	edgecolor="black"
	)
plt.title("Histogram of scores for Exam#1")
plt.xlabel("Exam#1: Points of 70")
plt.ylabel("Number of scores")
fig1.tight_layout()
imagePos1 += 1
saveFs1 = "./plot21-1-0{0:d}.png".format(imagePos1)
fig1.savefig(saveFs1,bbox_inches="tight")
savedImage1 = Image.open(saveFs1)
savedWidth1, savedHeight1= savedImage1.size
(_, _, _, _, _, _, savedSize1, _, savedTime1, _) = os.stat(saveFs1)
print("\t{0:s} : {1:d} x {2:d} , {3:,} bytes".format(saveFs1,savedWidth1,savedHeight1,savedSize1))

Here is the output of the Python code.

	./plot21-1-01.png : 630 x 470 , 17,791 bytes