从R中的文本文件中提取

Question

I need to compare two .txt files with the following formats , with R:

rows in file1:

1-11!AIVDM,1,1,,B,11b4N?@P?w<tSF0l4Q@>4?wp1`Oo,0*3D
 1347204643
2-12$GPRMC,153102,A,6300.774,N,05238.627,W,12.9,186,090912,30,W*79
 1347204664

( here for some reason the time (1347204643) is in the separate row)

rows in file2:

#1:1347204643:11!AIVDM,1,1,,B,11b4N?@P?w<tSF0l4Q@>4?wp1`Oo,0*3D
#2:1347204664:12$GPRMC,153102,A,6300.774,N,05238.627,W,12.9,186,090912,30,W*79

I am interested only in verifying if the same ID, which is in the beginning of the row (eg 1 and 2 here), exists in both files ( if the ID that exists in file1 exists also in file2).

Can someone help me with this? Thank you very much in advance!

Answer 1

You can do something like this :

First you read 2 two files using readLines

ll1 <- readLines(textConnection('#1:1347204643:11!AIVDM,1,1,,B,11b4N?@P?w<tSF0l4Q@>4?wp1`Oo,0*3D
#2:1347204664:12$GPRMC,153102,A,6300.774,N,05238.627,W,12.9,186,090912,30,W*79'))
ll2 <- readLines(textConnection('1-11!AIVDM,1,1,,B,11b4N?@P?w<tSF0l4Q@>4?wp1`Oo,0*3D
 1347204643
2-12$GPRMC,153102,A,6300.774,N,05238.627,W,12.9,186,090912,30,W*79
 1347204664'))

Do some treatments

#Remove '#` fom the first files
ll1 <- gsub('#','',ll1)
#Take only the odd lines from the second file
ll2 <- ll2[c(TRUE,FALSE)]

Extract the index of each lines using substr

ll1 <- substr(ll1,1,1)
ll2 <- substr(ll2,1,1)

Now you have this 2 lists :

ll1
[1] "1" "2"
> ll2
[1] "1" "2

To compare you can use match

match(ll1,ll2)
[1] 1 2