python 使用matplotlib.pyplot.hist繪制直方圖

一、直方圖(Histogram)介紹

直方圖，形狀類似柱狀圖卻有着與柱狀圖完全不同的含義。直方圖牽涉統計學的概念，首先要對數據進行分組，然后統計每個分組內數據元的數量。 在坐標系中，橫軸標出每個組的端點，縱軸表示頻數，每個矩形的高代表對應的頻數，稱這樣的統計圖為頻數分布直方圖。

相關概念：

• 組數：在統計數據時，我們把數據按照不同的范圍分成幾個組，分成的組的個數稱為組數
• 組距：每一組兩個端點的差

 

二、電影時長分布繪制

現有250部電影的時長,希望統計出這些電影時長的分布狀態(比如時長為100分鍾到120分鍾電影的數量,出現的頻率)等信息,你應該如何呈現這些數據?

 數據：

time =[131,  98, 125, 131, 124, 139, 131, 117, 128, 108, 135, 138, 131, 102, 107, 114, 119, 128, 121, 142, 127, 130, 124, 101, 110, 116, 117, 110, 128, 128, 115,  99, 136, 126, 134,  95, 138, 117, 111,78, 132, 124, 113, 150, 110, 117,  86,  95, 144, 105, 126, 130,126, 130, 126, 116, 123, 106, 112, 138, 123,  86, 101,  99, 136,123, 117, 119, 105, 137, 123, 128, 125, 104, 109, 134, 125, 127,105, 120, 107, 129, 116, 108, 132, 103, 136, 118, 102, 120, 114,105, 115, 132, 145, 119, 121, 112, 139, 125, 138, 109, 132, 134,156, 106, 117, 127, 144, 139, 139, 119, 140,  83, 110, 102,123,107, 143, 115, 136, 118, 139, 123, 112, 118, 125, 109, 119, 133,112, 114, 122, 109, 106, 123, 116, 131, 127, 115, 118, 112, 135,115, 146, 137, 116, 103, 144,  83, 123, 111, 110, 111, 100, 154,136, 100, 118, 119, 133, 134, 106, 129, 126, 110, 111, 109, 141,120, 117, 106, 149, 122, 122, 110, 118, 127, 121, 114, 125, 126,114, 140, 103, 130, 141, 117, 106, 114, 121, 114, 133, 137,  92,121, 112, 146,  97, 137, 105,  98, 117, 112,  81,  97, 139, 113,134, 106, 144, 110, 137, 137, 111, 104, 117, 100, 111, 101, 110,105, 129, 137, 112, 120, 113, 133, 112,  83,  94, 146, 133, 101,131, 116, 111,  84, 137, 115, 122, 106, 144, 109, 123, 116, 111,111, 133, 150]

效果:

 

 

1、matplotlib.pyplot.hist(x, bins=None, normed=None, **kwargs)

# 直方圖繪制

Parameters:    
x : (n,) array or sequence of (n,) arrays

bins : integer or sequence or ‘auto’, optional
組距

normed : bool, optional
以頻率顯示或者以頻數顯示,默認頻數,值1為頻率

2、分析

• 設置組距
• 設置組數（通常對於數據較少的情況，分為5~12組，數據較多，更換圖形顯示方式）
  • 通常設置組數會有相應公式：組數 = 極差/組距= (max-min)/bins

# 展現不同電影的時長分布狀態
plt.figure(figsize=(20, 8), dpi=100)

# 准備時長數據
time =[131,  98, 125, 131, 124, 139, 131, 117, 128, 108, 135, 138, 131, 102, 107, 114, 119, 128, 121, 142, 127, 130, 124, 101, 110, 116, 117, 110, 128, 128, 115,  99, 136, 126, 134,  95, 138, 117, 111,78, 132, 124, 113, 150, 110, 117,  86,  95, 144, 105, 126, 130,126, 130, 126, 116, 123, 106, 112, 138, 123,  86, 101,  99, 136,123, 117, 119, 105, 137, 123, 128, 125, 104, 109, 134, 125, 127,105, 120, 107, 129, 116, 108, 132, 103, 136, 118, 102, 120, 114,105, 115, 132, 145, 119, 121, 112, 139, 125, 138, 109, 132, 134,156, 106, 117, 127, 144, 139, 139, 119, 140,  83, 110, 102,123,107, 143, 115, 136, 118, 139, 123, 112, 118, 125, 109, 119, 133,112, 114, 122, 109, 106, 123, 116, 131, 127, 115, 118, 112, 135,115, 146, 137, 116, 103, 144,  83, 123, 111, 110, 111, 100, 154,136, 100, 118, 119, 133, 134, 106, 129, 126, 110, 111, 109, 141,120, 117, 106, 149, 122, 122, 110, 118, 127, 121, 114, 125, 126,114, 140, 103, 130, 141, 117, 106, 114, 121, 114, 133, 137,  92,121, 112, 146,  97, 137, 105,  98, 117, 112,  81,  97, 139, 113,134, 106, 144, 110, 137, 137, 111, 104, 117, 100, 111, 101, 110,105, 129, 137, 112, 120, 113, 133, 112,  83,  94, 146, 133, 101,131, 116, 111,  84, 137, 115, 122, 106, 144, 109, 123, 116, 111,111, 133, 150]
# 定義一個間隔大小
a = 2

# 得出組數
bins = int((max(time) - min(time)) / a)

# 畫出直方圖
plt.hist(time, bins, normed=1)

# 指定刻度的范圍，以及步長
plt.xticks(list(range(min(time), max(time)))[::2])

plt.xlabel("電影時長大小")
plt.ylabel("電影的數據量")

plt.grid(True, linestyle='--', alpha=0.5)

plt.show()

3、增加網格顯示

為了更好將圖形對應到

plt.grid(True, linestyle='--', alpha=0.5)