python_matplotlib
matplotliob.pyplotの使い方メモ
- 複数の図(subplot)の全体についてタイトルをつける:
plt.suptitle
- 複数の図(subplot)どうしの間隔を調整:
plt.subplots_adjust(wspace=0.4, hspace=0.6)
- 新規ウィンドウ(複数の図を別々のウィンドウで出す時) / Display two images in different windows
plt.imshow(im1) plt.figure() # <---- This is the key!!! plt.imshow(im2) plt.show()
- plt.show()せずにウィンドウをキャッシュから消す:
plt.close()
- RGB画像を出したいときは, データをnp.arrayでastype(uint8)にすること。uint16やfloatでは色が変になる。たとえvmin, vmaxを指定しても。
drawing a map (plt.imshow)
- change aspect (narrower, for example):
plt.imshow(img, aspect=2) # ... vertical length is 2 times of horizontal.
drawing a RGB map
plt.imshow(x[:,:,[4,2,1]]/np.max(x[:,:,[4,2,1]]))
- Here, x is np.ndarray with a shape of (lines, pixels, bands).
- The data must be represented by real numbers ranging from 0 to 1. No "int" or "uint", please!
- By setting the third index as [4, 2, 1], the band 4, band 2, and band 1 are assigned to R, G, B, respectively.
Label
- give title of the picture:
plt.title("title")
- x-axis label:
plt.xlabel("PRVI (dB)")
- y-axis label:
plt.ylabel("NDVI")
- erase labels:
plt.tick_params(labelbottom=False, labelleft=False, labelright=False, labeltop=False)
Color
- How to describe colors: https://pythondatascience.plavox.info/matplotlib/%E8%89%B2%E3%81%AE%E5%90%8D%E5%89%8D
- names of colors:
Colormap
- https://matplotlib.org/tutorials/colors/colormaps.html?highlight=colormap
- show the list of color maps:
help(matplotlib.cm)
- Change color table of a map:
plt.imshow(x, cmap=matplotlib.cm.gray) # このgrayのところをカラーテーブル名にする。
- Reverse the color map: Put "_r" at the end of the color map name.
plt.imshow(x, cmap=matplotlib.cm.rainbow_r)
Keyword(s):
References: