A3: matploblib 기본

Author

최규빈

Published

March 5, 2026

1. 강의영상

2. Imports

import matplotlib.pyplot as plt
plt.rcParams['figure.figsize'] = (4.5, 3.0)

3. Line plot

A. 기본플랏

- 예시1

x=[1,2,3,4]
y=[1,2,4,3] 
plt.plot(x,y)

모양변경

- 예시1

plt.plot(x,y,'--')

- 예시2

plt.plot(x,y,':')

- 예시3

plt.plot(x,y,'-.')

B. 색상변경

- 예시1

plt.plot(x,y,'r')

- 예시2

plt.plot(x,y,'k')

C. 모양 + 색상변경

- 예시1

plt.plot(x,y,'--r')

- 예시2: 순서변경 가능

plt.plot(x,y,'r--')

D. 원리?

- r--등의 옵션은 Markers + Line Styles + Colors 의 조합으로 표현가능

ref: https://matplotlib.org/stable/api/_as_gen/matplotlib.pyplot.plot.html

  • --r: 점선(dashed)스타일 + 빨간색
  • r--: 빨간색 + 점선(dashed)스타일
  • :k: 점선(dotted)스타일 + 검은색
  • k:: 검은색 + 점선(dotted)스타일

- 우선 Marker를 무시하면 Line Styles + Color로 표현가능한 조합은 \(4\times 8=32\) 개

(Line Styles) 모두 4개

character description
‘-’ solid line style
‘–’ dashed line style
‘-.’ dash-dot line style
‘:’ dotted line style

(Color) 모두 8개

character color
‘b’ blue
‘g’ green
‘r’ red
‘c’ cyan
‘m’ magenta
‘y’ yellow
‘k’ black
‘w’ white

- 예시1

plt.plot(x,y,'--m')

- 예시2

plt.plot(x,y,'-.c')

- 예시3: line style + color 조합으로 사용하든 color + line style 조합으로 사용하든 상관없음

plt.plot(x,y,'-.c')

plt.plot(x,y,'c-.')

- 예시4: line style을 중복으로 사용하거나 color를 중복으로 쓸 수 는 없다.

plt.plot(x,y,'--:')
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
Cell In[17], line 1
----> 1 plt.plot(x,y,'--:')

File ~/Dropbox/02-lec/2026-03-딥러닝/.venv/lib/python3.10/site-packages/matplotlib/pyplot.py:3838, in plot(scalex, scaley, data, *args, **kwargs)
   3830 @_copy_docstring_and_deprecators(Axes.plot)
   3831 def plot(
   3832     *args: float | ArrayLike | str,
   (...)
   3836     **kwargs,
   3837 ) -> list[Line2D]:
-> 3838     return gca().plot(
   3839         *args,
   3840         scalex=scalex,
   3841         scaley=scaley,
   3842         **({"data": data} if data is not None else {}),
   3843         **kwargs,
   3844     )

File ~/Dropbox/02-lec/2026-03-딥러닝/.venv/lib/python3.10/site-packages/matplotlib/axes/_axes.py:1777, in Axes.plot(self, scalex, scaley, data, *args, **kwargs)
   1534 """
   1535 Plot y versus x as lines and/or markers.
   1536 
   (...)
   1774 (``'green'``) or hex strings (``'#008000'``).
   1775 """
   1776 kwargs = cbook.normalize_kwargs(kwargs, mlines.Line2D)
-> 1777 lines = [*self._get_lines(self, *args, data=data, **kwargs)]
   1778 for line in lines:
   1779     self.add_line(line)

File ~/Dropbox/02-lec/2026-03-딥러닝/.venv/lib/python3.10/site-packages/matplotlib/axes/_base.py:297, in _process_plot_var_args.__call__(self, axes, data, return_kwargs, *args, **kwargs)
    295     this += args[0],
    296     args = args[1:]
--> 297 yield from self._plot_args(
    298     axes, this, kwargs, ambiguous_fmt_datakey=ambiguous_fmt_datakey,
    299     return_kwargs=return_kwargs
    300 )

File ~/Dropbox/02-lec/2026-03-딥러닝/.venv/lib/python3.10/site-packages/matplotlib/axes/_base.py:444, in _process_plot_var_args._plot_args(self, axes, tup, kwargs, return_kwargs, ambiguous_fmt_datakey)
    441 if len(tup) > 1 and isinstance(tup[-1], str):
    442     # xy is tup with fmt stripped (could still be (y,) only)
    443     *xy, fmt = tup
--> 444     linestyle, marker, color = _process_plot_format(
    445         fmt, ambiguous_fmt_datakey=ambiguous_fmt_datakey)
    446 elif len(tup) == 3:
    447     raise ValueError('third arg must be a format string')

File ~/Dropbox/02-lec/2026-03-딥러닝/.venv/lib/python3.10/site-packages/matplotlib/axes/_base.py:167, in _process_plot_format(fmt, ambiguous_fmt_datakey)
    165 if fmt[i:i+2] in mlines.lineStyles:  # First, the two-char styles.
    166     if linestyle is not None:
--> 167         raise ValueError(errfmt.format(fmt, "two linestyle symbols"))
    168     linestyle = fmt[i:i+2]
    169     i += 2

ValueError: '--:' is not a valid format string (two linestyle symbols)

plt.plot(x,y,'rb')

- 예시5: 색이 사실 8개만 있는건 아니다.

ref: https://matplotlib.org/2.0.2/examples/color/named_colors.html

plt.plot(x,y,'--',color='lime')

- 예시6: 색을 바꾸려면 Hex코드를 밖아 넣는 방법이 젤 깔끔함

ref: https://htmlcolorcodes.com/

plt.plot(x,y,color='#277E41')

- 예시7: 당연히 라인스타일도 4개만 있진 않겠지

ref: https://matplotlib.org/stable/gallery/lines_bars_and_markers/linestyles.html

plt.plot(x,y,linestyle='dashed')

plt.plot(x,y,linestyle=(0, (20, 5)))

4. Scatter plot

A. 원리

- 그냥 마커를 설정하면 끝!

ref: https://matplotlib.org/stable/api/_as_gen/matplotlib.pyplot.plot.html

character description
‘.’ point marker
‘,’ pixel marker
‘o’ circle marker
‘v’ triangle_down marker
‘^’ triangle_up marker
‘<’ triangle_left marker
‘>’ triangle_right marker
‘1’ tri_down marker
‘2’ tri_up marker
‘3’ tri_left marker
‘4’ tri_right marker
‘8’ octagon marker
‘s’ square marker
‘p’ pentagon marker
‘P’ plus (filled) marker
’*’ star marker
‘h’ hexagon1 marker
‘H’ hexagon2 marker
‘+’ plus marker
‘x’ x marker
‘X’ x (filled) marker
‘D’ diamond marker
‘d’ thin_diamond marker
‘|’ vline marker
’_’ hline marker 
plt.plot(x,y,'o')

B. 기본플랏

- 예시1

plt.plot(x,y,'.')

- 예시2

plt.plot(x,y,'x')

C. 색깔변경

- 예시1

plt.plot(x,y,'or')

- 예시2

plt.plot(x,y,'db')

- 예시3

plt.plot(x,y,'bx')

D. dot-connected plot

- 예시1: 마커와 라인스타일을 동시에 사용하면 dot-connected plot이 된다.

plt.plot(x,y,'o-')

- 예시2: 당연히 색도 적용가능함

plt.plot(x,y,'o--r')

- 예시3: 서로 순서를 바꿔도 상관없다.

plt.plot(x,y,'ro--')