fundamental

• Basic usage

  Axes will take some getting used to

                  import matplotlib.pyplot as plt
                  fig=plt.figure()
                  ax=fig.add_subplot(111)
                  ax.plot([1,2],[1,2])
                  plt.show()

  

• mark with a dot (point)

                  import matplotlib.pyplot as plt
                  fig=plt.figure()
                  ax=fig.add_subplot(111)
                  ax.plot([1,2],[1,2],marker="o")

  

• Change line style

                  import matplotlib.pyplot as plt
                  fig=plt.figure()
                  ax=fig.add_subplot(111)
                  ax.plot([1,2],[1,2],linestyle="dashed",color="tab:orange")

  
  If you set None instead of dashed, the lines disappear

• Change line thickness and dot size

                  import matplotlib.pyplot as plt
                  fig=plt.figure()
                  ax=fig.add_subplot(111)
                  ax.plot([1,2],[1,2],marker="o",linewidth=3,markersize=15)

  

• Name the axes

                  import matplotlib.pyplot as plt
                  fig=plt.figure()
                  ax=fig.add_subplot(111)
                  ax.plot([1,2],[0,24])
                  ax.set_xlabel("day",labelpad=5)
                  ax.set_ylabel("hour",labelpad=10)

  
  how far away from the axis the label pad is (optional)

• Size and Range Specification

                  import matplotlib.pyplot as plt
                  fig=plt.figure(figsize=(10,4))
                  ax=fig.add_subplot(111)
                  ax.plot([1,2],[1,2])
                  ax.set_xlim(1,5)
                  ax.set_ylim(0,3)

  

• give a legend

                  import matplotlib.pyplot as plt
                  import numpy as np
                  t=np.linspace(0,10,100)
                  fig=plt.figure()
                  ax=fig.add_subplot(111)
                  ax.plot(t,np.sin(t),label="sin(t)")
                  ax.plot(t,np.cos(t),label="cos(t)")
                  ax.legend()

  

• Insert text anywhere

  With transform=ax.transAxes, you can specify coordinates relative to the graph box instead of coordinates on the graph.

                  import matplotlib.pyplot as plt
                  import numpy as np
                  t=np.linspace(0,10,100)
                  fig=plt.figure()
                  ax=fig.add_subplot(111)
                  ax.plot(t,np.sin(t),label="sin(t)")
                  ax.text(0.02,0.95,"(a)",transform=ax.transAxes)
                  ax.set_xlabel("t")

  

• Use the left and right axes

                  import matplotlib.pyplot as plt
                  import numpy as np
                  t=np.linspace(0,10,100)
                  fig=plt.figure()
                  ax1=fig.add_subplot(111)
                  ax1.plot(t,np.sin(t),color="tab:blue")
                  ax1.set_xlabel("t")
                  ax1.set_ylabel("sin(t)")
                  ax2=ax1.twinx()
                  ax2.plot(t,np.tan(t),color="tab:orange")
                  ax2.set_ylim(-10,10)
                  ax2.set_ylabel("tan(t)")

  

• Use left and right axes, add common legend

                  import matplotlib.pyplot as plt
                  import numpy as np
                  t=np.linspace(0,10,100)
                  fig=plt.figure()
                  ax1=fig.add_subplot(111)
                  ln1=ax1.plot(t,np.sin(t),color="tab:blue",label="sin(t)")
                  ax1.set_xlabel("t")
                  ax1.set_ylabel("sin(t)")
                  ax2=ax1.twinx()
                  ln2=ax2.plot(t,np.tan(t),color="tab:orange",label="tan(t)")
                  ax2.set_ylim(-10,10)
                  ax2.set_ylabel("tan(t)")
                  ln=ln1+ln2
                  lab=[l.get_label() for l in ln]
                  ax2.legend(ln,lab,loc=4)

  
  loc=1 (top right), 2 (top left), 3 (bottom left), 4 (bottom right)

• Save the file

  Install dvipng and cm-super

                  sudo apt update
                  sudo apt install cm-super
                  sudo apt install dvipng

                plt.savefig("hoge.pdf")

  To minimize margins

                  plt.savefig("hoge.pdf",bbox_inches="tight",pad_inches=0)

  If you set pad_inchdes to 0, it may be just barely cut when using png, etc. In that case, put a smaller value. If you want a transparent background, set transparent=True.

Character-related

• LaTeX Specifications

                  import matplotlib.pyplot as plt
                  import numpy as np
                  t=np.linspace(0,5,100)
                  fig=plt.figure()
                  ax=fig.add_subplot(111)
                  ax.plot(t,np.exp(-t)*np.sin(t))
                  ax.set_title(r"$x=e^{-t} \sin 5t$")
                  ax.set_xlabel(r"$t$")
                  ax.set_ylabel(r"$x$")

  

• Full LaTeX specification

                  import matplotlib as mpl
                  import matplotlib.pyplot as plt
                  import numpy as np
                  t=np.linspace(0,5,100)
                  mpl.rc("text",usetex=True)
                  mpl.rcParams["text.latex.preamble"]= r"\usepackage{cmbright,amsmath,amssymb}" 
                  fig=plt.figure()
                  ax=fig.add_subplot(111)
                  ax.plot(t,np.exp(-t)*np.sin(t))
                  ax.set_title(r"$x=e^{-t} \sin 5t$")
                  ax.set_xlabel(r"$t$")
                  ax.set_ylabel(r"$x$")

  

• Change font size

                  import matplotlib as mpl
                  import matplotlib.pyplot as plt
                  import numpy as np
                  t=np.linspace(0,5,100)
                  mpl.rcParams["font.size"]=16
                  fig=plt.figure()
                  ax=fig.add_subplot(111)
                  ax.plot(t,np.exp(-t)*np.sin(t))
                  ax.set_title(r"$x=e^{-t} \sin 5t$")
                  ax.set_xlabel(r"$t$")
                  ax.set_ylabel(r"$x$")

  

• Use Japanese

                  import matplotlib as mpl
                  import matplotlib.pyplot as plt
                  import numpy as np
                  t=np.linspace(0,5,100)
                  mpl.rcParams["font.family"]="IPAexGochic"
                  fig=plt.figure()
                  ax=fig.add_subplot(111)
                  ax.plot(t,np.exp(-t)*np.sin(t))
                  ax.set_title(r"$x=e^{-t} \sin 5t$のグラフ")
                  ax.set_xlabel("時間")
                  ax.set_ylabel("減衰振動")

  

• Using Japanese in LaTeX Specifications

                  import matplotlib as mpl
                  import matplotlib.pyplot as plt
                  import numpy as np
                  t=np.linspace(0,5,100)
                  mpl.rc("text",usetex=True)
                  mpl.rcParams["text.latex.preamble"]= r"\usepackage{cmbright,amsmath,amssymb}" r"\usepackage[whole]{bxcjkjatype}" 
                  fig=plt.figure()
                  ax=fig.add_subplot(111)
                  ax.plot(t,np.exp(-t)*np.sin(t))
                  ax.set_title(r"$x=e^{-t} \sin 5t$のグラフ")
                  ax.set_xlabel("時間")
                  ax.set_ylabel("減衰振動")

  

data loading

• Binary file loading

                  import numpy as np
                  f=open("hoge.bin")
                  data=np.fromfile(f,dtype="f8",sep="")

• Reading ASCII files

  I think pandas.read_table reads ascii files rather smarter than numpy.genfromtxt. If necessary, then use numpy.array to make it into an array.

                  import numpy as np
                  import pandas as pd
                  data=pd.read_table("hoge.dat",sep="\s+",header=None)
                  data=np.array(data)