R - 识别连续序列 [英] R - identify consecutive sequences

问题描述

我有一个包含 107635 行和 3 列的大文件:主题、感兴趣区域 (ROI) 和试验次数.ROI 可以是 A、B、C、D、E、F.我想要做的是只保留那些在 ROI 列中我有 B、C、D 连续序列的试验，当 B 第一次出现时.B、C 和 D 出现多少次并不重要.

I have a big file with 107635 rows, and 3 columns: subject, regions of interest (ROIs), and number of the trial. The ROIs can be A, B, C, D, E, F. What I want to do is to keep only those trials where in the column ROI I have a consecutive sequence of B, C, D, the first time that B appears. It doesn't matter how many times B, C and D occur.

在下面的例子中，我可以保留 ntrial 78 和 201，因为第一次出现 B 之后是 C 和 D.但是，我需要删除ntrial 10 和400.在trial 10 中，B、C 和D 不连续.审判400中B第一次出现，B后面没有C和D.

In the example below, I can keep ntrial 78 and 201, because the first time that B appeared was followed by C and D. However, I need to remove the ntrial 10 and 400. In the trial 10 B, C and D are not consecutive. In the trial 400 the first time that B appears, B is not followed by C and D.

对于输出，我只需要一个值为 1 的列来保留每一行中的试验，并为与要删除的试验对应的行设置一个值为 0.

For the output, I just need a column with a value of 1 for the trials to keep, in each row, and a value of 0 for the rows corresponding to the trials to remove.

关于如何创建可以自动化程序的代码，而无需目视检查每次试验的任何建议?

Any suggestion on how to create a code that can automatise the procedure, without visually inspect each trial?

非常感谢！

subject ROI ntrial output
sbj05   A   78     1
sbj05   A   78     1
sbj05   A   78     1
sbj05   A   78     1
sbj05   A   78     1
sbj05   A   78     1
sbj05   B   78     1
sbj05   B   78     1
sbj05   C   78     1
sbj05   D   78     1
sbj05   E   78     1
sbj05   E   78     1
sbj05   E   78     1
sbj05   A   201    1
sbj05   A   201    1
sbj05   A   201    1
sbj05   A   201    1
sbj05   A   201    1
sbj05   B   201    1
sbj05   C   201    1
sbj05   D   201    1
sbj05   E   201    1
sbj05   E   201    1
sbj05   E   201    1
sbj05   F   201    1
sbj05   F   201    1
sbj05   A   10     0
sbj05   A   10     0
sbj05   A   10     0
sbj05   A   10     0
sbj05   B   10     0
sbj05   A   10     0
sbj05   C   10     0
sbj05   D   10     0
sbj05   E   10     0
sbj05   E   10     0
sbj05   A   400    0
sbj05   A   400    0
sbj05   A   400    0
sbj05   B   400    0
sbj05   A   400    0
sbj05   B   400    0
sbj05   C   400    0
sbj05   C   400    0
sbj05   C   400    0
sbj05   D   400    0
sbj05   E   400    0
sbj05   E   400    0
sbj05   D   400    0

推荐答案

这是使用 data.table 和 stringi

首先，我定义了一些辅助函数，它可以帮助我检测每组 B 的第一次准确率，并验证它们后面的序列是否正确

First, I'm defining some helper function that will help me detect first accurances of B per group and validate that they are followed by the correct sequence

Myfunc <- function(x) {
               which(x == "B")[1L] == 
               stri_locate_first_regex(paste(x, collapse = ""), 'B*CD')[, 1L]
              } 

然后，实现是直截了当的

Then, the implementation is straight forward

library(data.table)
library(stringi)
setDT(df)[, if(Myfunc(ROI)) .SD, by = .(subject, ntrial)]
#     subject ntrial ROI
#  1:   sbj05     78   A
#  2:   sbj05     78   A
#  3:   sbj05     78   A
#  4:   sbj05     78   A
#  5:   sbj05     78   A
#  6:   sbj05     78   A
#  7:   sbj05     78   B
#  8:   sbj05     78   B
#  9:   sbj05     78   C
# 10:   sbj05     78   D
# 11:   sbj05     78   E
# 12:   sbj05     78   E
# 13:   sbj05     78   E
# 14:   sbj05    201   A
# 15:   sbj05    201   A
# 16:   sbj05    201   A
# 17:   sbj05    201   A
# 18:   sbj05    201   A
# 19:   sbj05    201   B
# 20:   sbj05    201   C
# 21:   sbj05    201   D
# 22:   sbj05    201   E
# 23:   sbj05    201   E
# 24:   sbj05    201   E
# 25:   sbj05    201   F
# 26:   sbj05    201   F

<小时>

或者，如果你只想要一个额外的列，你可以做

---

Or, if you just want an additional column you could do

setDT(df)[, output := +Myfunc(ROI), by = .(subject, ntrial)]

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