从分组值的子集创建matplotlib图表时，For循环中出现ValueError

Question

我的数据源已更改，更新从分组数据创建绘图的代码时遇到问题。我能够成功地绘制数据的一个子集，但是我需要添加一个条件，在同一个图表上绘制两个子集。有没有一种方法可以让我的for/if/elif实现这一点

This is what works

但是，处理过的\u-eye值同时包含OD和OS，我需要在同一个图表上绘制它们：当OD时，我需要绘制*\u-OD列值，当OS时，我需要绘制*\u-OS列值，因此我修改了代码并得到一个值错误：

# plot for new data
for subject_group, sub_df in new_df.groupby(by='subject_group'):
    if new_df.treated_eye == 'OD':
        plt.plot(sub_df['visit_number'], sub_df['white_od'], marker='o', label=subject_group)
    elif new_df.treated_eye == 'OS':
        plt.plot(sub_df['visit_number'], sub_df['white_os'], marker='o', label=subject_group)

plt.legend(bbox_to_anchor=(1.05, 1), loc=2, borderaxespad=0.)

# add a normal line at -65
# plt.ylim(ymin=-70, ymax=-30) # add ymax to make both color plots consistent
plt.xticks(range(0, new_od_df['visit_number'].max() + 1 , 1))

plt.xlabel('Visit (Months)')
plt.ylabel('Threshold (dB)')

# add a dashed green line and "normal"
plt.axhline(-65, color="green", linestyle='--', dashes=(5, 10)) #length of 5, space of 10
plt.text(13, -65, 'Normal', va='center', ha="left", bbox=dict(facecolor="w",alpha=0.5))


plt.title('RPGR-001: White FST (Treated Eye)')
plt.tight_layout()
# plt.savefig('output/rpgr_fst_white_teye.png')

ValueError Traceback (most recent call last) in () 1 # plot for new data 2 for subject_group, sub_df in new_df.groupby(by='subject_group'): ----> 3 if new_df.treated_eye == 'OD': 4 plt.plot(sub_df['visit_number'], sub_df['white_od'], marker='o', label=subject_group) 5 elif new_df.treated_eye == 'OS':

~\AppData\Local\Continuum\anaconda3\lib\site-packages\pandas\core\generic.py in nonzero(self) 1574 raise ValueError("The truth value of a {0} is ambiguous. " 1575 "Use a.empty, a.bool(), a.item(), a.any() or a.all()." -> 1576 .format(self.class.name)) 1577 1578 bool = nonzero

ValueError: The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().

Answer 1

问题不在于matplotlib，而在于if语句new_df.treated_eye和new_df.treated_eye是数据帧中包含多个条目的列。当您执行if new_df.treated_eye == 'OD'时，当new_df.treated_eye是一个列表时，您将其视为一个变量。由于要在所有元素满足此条件时进行绘图，因此需要使用all()

因此，请尝试以下方法

for subject_group, sub_df in new_df.groupby(by='subject_group'):
    if all(new_df.treated_eye == 'OD'):
        plt.plot(sub_df['visit_number'], sub_df['white_od'], marker='o', label=subject_group)
    elif all(new_df.treated_eye == 'OS'):
        plt.plot(sub_df['visit_number'], sub_df['white_os'], marker='o', label=subject_group)