StringCases using RegularExpression fails when there is missing data

Question

I got some text scraps with this structure

"Focal Plane: 198'  Active Aid to Navigation: Yes  *Latitude: 35.250 N  *Longitude: -75.529 W"

But some of them lack of parts like this

"Focal Plane: 198'  Active Aid to Navigation: Yes  *Longitude: -75.529 W"

Using regular expression matching, I want to extract all the info available, included getting a tag "NotAvailable" for missing data.,

I wrote this code, but it can't tell when a pattern does not match -- should the pattern in the middle not match, my code just skips it and goes on to the next pattern:

ptrFocal = "(?<=\\Focal Plane: )(.*?)(?=\\')";
ptrLat = "(?<=\\*Latitude: )(.*?)(?=[a-zA-Z])";
ptrLon = "(?<=\\*Longitude: )(.*?)(?=[a-zA-Z])";

r = 
  StringTrim /@ StringCases[text, 
    RegularExpression[ptrFocal <> "|" <> ptrLat <> "|" <> ptrLon]
  ];

I would want some pointers on how to do this.

EDIT:

The expected transformation of the example data I gave above is

{198, 32.250, -75.529}
{198, "NotAvailable", -75.529}

Answer 1

str1 = "Focal Plane: 198' Active Aid to Navigation: Yes *Latitude: \
35.250 N *Longitude: -75.529 W";

str2 = "Focal Plane: 198.12' Active Aid to Navigation: Yes \
*Longitude: -75.529 W"

With string patterns because I do not use regex :)

record[string_] := Map[
   StringCases[string, # ~~ x : NumberString :> x] /. {} -> "NotAvailable" &,
   {"Focal Plane: ", "Latitude: ", "Longitude: "}] // Flatten

record@str1

record@str2

{"198", "35.250", "-75.529"}
{"198.12", "NotAvailable", "-75.529"}

You can add ToExpression /@ StringCases[... if you need numbers not strings.

Answer 2

A variation of Kuba's method, using a single StringCases pass with post processing:

str2 = "Focal Plane: 198.12' Active Aid to Navigation: Yes *Longitude: -75.529 W"

fields = {"Focal Plane: ", "Latitude: ", "Longitude: "};

StringCases[str2, a : fields ~~ x : NumberString :> (a -> ToExpression[x])]
fields /. % /. _String :> "NotAvailable"

"Focal Plane: 198.12' Active Aid to Navigation: Yes *Longitude: -75.529 W"

{"Focal Plane: " -> 198.12, "Longitude: " -> -75.529}

{198.12, "NotAvailable", -75.529}

Answer 3

As requested, here is one approach using pure RegularExpression.

Another difference is the use of Internal`StringToDouble that is faster then ToExpression (velocity test here).

getFields[str_String]:=Module[{fields,r},
    fields = {"Focal Plane: ", "Latitude: ", "Longitude: "};    
    r=Map[StringCases[str,RegularExpression[#<>"((\\+|-)?\\d+(\\.\\d+)?)"]:>Internal`StringToDouble@"$1"]&,fields];
    r=Flatten[r/.{}-> Missing]
]

str1 = "Focal Plane: 198.23'  Active Aid to Navigation: Yes   *Longitude: -75.529 W";
str2 = "Focal Plane: 198.23'  Active Aid to Navigation: Yes  *Latitude: 35.250 N  *Longitude: -75.529 W";

getFields@str1
getFields@str2

{198.23, Missing, -75.529}

{198.23, 35.25`, -75.529}