[R] parsing numeric values

[baptiste auguie]

Dear list,

I'm seeking advice to extract some numeric values from a log file
created by an external program. Consider the following example,

input <-
readLines(textConnection(
"some text
  <ax> =    1.3770E-03     <bx> =    3.4644E-07
  <ay> =    1.9412E-04     <by> =    4.8840E-08

other text
  <aax>  =    1.3770E-03     <bbx> =    3.4644E-07
  <aay>  =    1.9412E-04     <bby> =    4.8840E-08"))

## this is what I want
results <- c(as.numeric(strsplit(grep("<ax>", input,val=T), " ")[[1]][8]),
             as.numeric(strsplit(grep("<ay>", input,val=T), " ")[[1]][8]),
             as.numeric(strsplit(grep("<aax>", input,val=T), " ")[[1]][9]),
             as.numeric(strsplit(grep("<aay>", input,val=T), " ")[[1]][9])
             )

## [1] 0.00137700 0.00019412 0.00137700 0.00019412

The use of strsplit is not ideal here as there is a different number
of space characters in the lines containing <ax> and <aax> for
instance (hence the indices 8 and 9 respectively).

I tried to use gsubfn for a cleaner construct,

strapply(input, "<ax> += +([0-9.]+)", c, simplify=rbind,combine=as.numeric)

but I can't seem to find the correct regular expression to deal with
the exponent.


Any tips are welcome!


Best regards,

baptiste