Pandas以降序绘制x或index_column [英] Pandas plot x or index_column in descending order
问题描述
我想根据化学分析中导入的csv文件做一些绘图。所以我导入如下:
I wanted to do some plots based on imported csv files from a chemical analysis. So I import as follows:
In [91]:
df = pd.read_csv('/file_location/Untitled 1.csv', delimiter = '\;', index_col = 'IR')
df
Out[91]:
Sample 1 Sample 2
IR
300 1 0
400 5 4
500 6 0
600 0 8
4 rows × 2 columns
In [98]:
df.plot()
精细看起来很好。
按照惯例,我用x轴以降序绘制这种类型的数据。最右边的数字(不要问我为什么)。所以我重新排序index-col:
By convention this type of data i plotted with the x axis in descending order. Highest number to the right (do not ask me why). So i reorder the index-col:
In [97]:
df2 = df.sort_index(axis=0, ascending=False, kind='quicksort')
df2
Out[97]:
Sample 1 Sample 2
IR
600 0 8
500 6 0
400 5 4
300 1 0
4 rows × 2 columns
太棒了!
In [96]:
df2.plot()
Out[96]:
但是当我绘制它看起来一样(/ sadpanda)
But when i Plot it looks the same (/sadpanda)
任何想法=)?
推荐答案
另一种方法是是在matplotlib中反转x轴的方向。这里代码的关键位是 plt.gca()。invert_xaxis()
。注意:这会将x轴保留为整数轴。示例代码如下:
Another approach would be to invert the direction of the x-axis in matplotlib. The key bit of code here is plt.gca().invert_xaxis()
. Note: this leaves the x-axis as an integer axis. Example code follows:
from StringIO import StringIO # for python 2.7; import from io for python 3
import pandas as pd
import matplotlib.pyplot as plt
# get data
data = """,sample1, sample2
300, 1, 0
400, 5, 4
500, 6, 0
600, 0, 8"""
df = pd.read_csv(StringIO(data), header=0, index_col=0, skipinitialspace=True)
# and plot
df.plot()
plt.gca().invert_xaxis()
plt.show()
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