我有一个大数据文件，并且我只对具有特定x值4.125的行感兴趣，如下所示。现在，因为4.125的值与离子的停止位置有关，所以我也很感兴趣相应的开始位置，因此我想将此信息保留在数组中。
如何编写一个程序，该程序可以有效地找到4.125的x停止位置并保留离子的起始位置？
这是一个120982 * 9数组，在下面显示的示例中，我希望保留离子＃3849096的信息。
"Ion N","Mass","Charge","X","Y","Z","Azm","Elv","KE"
3849094,0.00054858,-1,66.5216,-51,-3.8,-180,88.7,18160
3849094,0.00054858,-1,27.3925,30.3532,-4.07076,-177.1,41.5494,17697.2
3849095,0.00054858,-1,66.5216,-51,-3.7,-180,88.7,18160
3849095,0.00054858,-1,26.6277,31.0039,-3.91402,-177.096,40.8293,17699.4
3849096,0.00054858,-1,66.5216,-51,-3.6,-180,88.7,18160
3849096,0.00054858,-1,4.125,44.9887,-2.47517,-176.363,25.715,17711.1
这是我到目前为止开发的代码，但是不起作用：
import pandas as pd
import numpy as np
opts = pd.read_csv('Ambre_2.dat',sep = ',', low_memory = False)
df = pd.DataFrame(opts)
X = df.iloc[:,3]
IonN = df.iloc[:,0]
tol = 1e-6
Fltr = 4.125
filterreddata = df[abs(df['X'] - Fltr) < tol]
filteredions = df[np.in1d(df['Ion N'], filterreddata['Ion N'])]
filteredions[2:2:end, :] = []
f = open('ions.csv', 'w')
f.write(tabulate(filteredions))
f.close()
ions.csv文件应如下所示：
"Ion N","Mass","Charge","X","Y","Z","Azm","Elv","KE"
348450 0.00054858 -1 50.2216 -41 0.9 0 88.1 9200
348451 0.00054858 -1 50.3216 -41 0.9 0 88.1 9200
348511 0.00054858 -1 50.2216 -41 1 0 88.1 9200
348512 0.00054858 -1 50.3216 -41 1 0 88.1 9200