从大CSV过滤数据

Question

我有一个大的数据文件，我只对x值为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，相应的起始位置我也很感兴趣，我想把这个信息保存在数组中。在

如何编写一个程序，有效地找到4.125的x停止位置并保留离子开始位置？在

它是一个120982 * 9数组，在下面所示的例子中，我希望保留离子{}的信息。在

"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

这是我迄今为止开发的代码，但不起作用：

^{pr2}$

在离子.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