使用自定义滴答的散点图(Scatter plot with custom ticks)

 我想在y轴和光谱类（字符/字符串列表）在x轴，标签= ['B'，'A'，'F'，'G' ， 'K'， 'M'。 数据保存在熊猫数据框中，df。 
 
df['Spec Type Index']
0      NaN
1        A
2        G
.        .
.        .
167      K
168    Nan
169      G
 
 然后， 
 
df['Disk Major Axis "']
0        4.30
1        4.50
2       22.00
.         .
.         .
167      1.32
168      0.28
169     25.00
 
 因此，我认为这应该简单地用 
 
plt.scatter(df['Spec Type Index'], df['Disk Major Axis "'])
 
 但我得到这个令人讨厌的错误 
 
 
 
 无法将字符串转换为浮点型：'G' 
 
 
 解决这个问题之后，我想按如下方式制作自定义xticks。 但是，我怎么能 
 
labels = ['B','A','F','G','K','M']
ticks = np.arange(len(labels))
plt.xticks(ticks, labels)

I want to do a scatter plot of a wavelength (float) in y-axis and spectral class (list of character/string) in x-axis, labels = ['B','A','F','G','K','M']. Data are saved in pandas dataframe, df.
 
df['Spec Type Index']
0      NaN
1        A
2        G
.        .
.        .
167      K
168    Nan
169      G
 
Then,
 
df['Disk Major Axis "']
0        4.30
1        4.50
2       22.00
.         .
.         .
167      1.32
168      0.28
169     25.00
 
Thus, I thought this should be done simply with
 
plt.scatter(df['Spec Type Index'], df['Disk Major Axis "'])
 
But I get this annoying error
 
 
 
could not convert string to float: 'G'
 
 
After fixing this, I want to make custom xticks as follows. However, how can I 
 
labels = ['B','A','F','G','K','M']
ticks = np.arange(len(labels))
plt.xticks(ticks, labels)

原文：https://stackoverflow.com/questions/37041758