Text processing/2
You are encouraged to solve this task according to the task description, using any language you may know.
The following data shows a few lines from the file readings.txt (as used in in the Data Munging task).
The data comes from a pollution monitoring station with twenty four instruments monitoring twenty four aspects of pollution in the air. periodically a record is added to the file constituting a line of 49 white-space separated fields, where white-space can be one or more space or tab characters.
The fields (from the left) are:
DATESTAMP [ VALUEn FLAGn ] * 24
i.e. a datestamp followed by twenty four repetitions of a floating point instrument value and that instruments associated integer flag. Flag values are >= 1 if the instruments is working and < 1 if their is some problem with that instrument in which case that instruments value should be ignored.
A sample from the full data file readings.txt is:
1991-03-30 10.000 1 10.000 1 10.000 1 10.000 1 10.000 1 10.000 1 10.000 1 10.000 1 10.000 1 10.000 1 10.000 1 10.000 1 10.000 1 10.000 1 10.000 1 10.000 1 10.000 1 10.000 1 10.000 1 10.000 1 10.000 1 10.000 1 10.000 1 10.000 1 1991-03-31 10.000 1 10.000 1 10.000 1 10.000 1 10.000 1 10.000 1 10.000 1 20.000 1 20.000 1 20.000 1 35.000 1 50.000 1 60.000 1 40.000 1 30.000 1 30.000 1 30.000 1 25.000 1 20.000 1 20.000 1 20.000 1 20.000 1 20.000 1 35.000 1 1991-03-31 40.000 1 0.000 -2 0.000 -2 0.000 -2 0.000 -2 0.000 -2 0.000 -2 0.000 -2 0.000 -2 0.000 -2 0.000 -2 0.000 -2 0.000 -2 0.000 -2 0.000 -2 0.000 -2 0.000 -2 0.000 -2 0.000 -2 0.000 -2 0.000 -2 0.000 -2 0.000 -2 0.000 -2 1991-04-01 0.000 -2 13.000 1 16.000 1 21.000 1 24.000 1 22.000 1 20.000 1 18.000 1 29.000 1 44.000 1 50.000 1 43.000 1 38.000 1 27.000 1 27.000 1 24.000 1 23.000 1 18.000 1 12.000 1 13.000 1 14.000 1 15.000 1 13.000 1 10.000 1 1991-04-02 8.000 1 9.000 1 11.000 1 12.000 1 12.000 1 12.000 1 27.000 1 26.000 1 27.000 1 33.000 1 32.000 1 31.000 1 29.000 1 31.000 1 25.000 1 25.000 1 24.000 1 21.000 1 17.000 1 14.000 1 15.000 1 12.000 1 12.000 1 10.000 1 1991-04-03 10.000 1 9.000 1 10.000 1 10.000 1 9.000 1 10.000 1 15.000 1 24.000 1 28.000 1 24.000 1 18.000 1 14.000 1 12.000 1 13.000 1 14.000 1 15.000 1 14.000 1 15.000 1 13.000 1 13.000 1 13.000 1 12.000 1 10.000 1 10.000 1
The task:
- Confirm the general field format of the file
- Identify any DATASTAMPs that are duplicated.
- What number of records have good readings for all instruments.
Ada
<ada> with Ada.Calendar; use Ada.Calendar; with Ada.Text_IO; use Ada.Text_IO; with Strings_Edit; use Strings_Edit; with Strings_Edit.Floats; use Strings_Edit.Floats; with Strings_Edit.Integers; use Strings_Edit.Integers;
with Generic_Map;
procedure Data_Munging_2 is
package Time_To_Line is new Generic_Map (Time, Natural); use Time_To_Line; File : File_Type; Line_No : Natural := 0; Count : Natural := 0; Stamps : Map;
begin
Open (File, In_File, "readings.txt"); loop declare Line : constant String := Get_Line (File); Pointer : Integer := Line'First; Flag : Integer; Year, Month, Day : Integer; Data : Float; Stamp : Time; Valid : Boolean := True; begin Line_No := Line_No + 1; Get (Line, Pointer, SpaceAndTab); Get (Line, Pointer, Year); Get (Line, Pointer, Month); Get (Line, Pointer, Day); Stamp := Time_Of (Year_Number (Year), Month_Number (-Month), Day_Number (-Day)); begin Add (Stamps, Stamp, Line_No); exception when Constraint_Error => Put (Image (Year) & Image (Month) & Image (Day) & ": record at " & Image (Line_No)); Put_Line (" duplicates record at " & Image (Get (Stamps, Stamp))); end; for Reading in 1..24 loop Get (Line, Pointer, SpaceAndTab); Get (Line, Pointer, Data); Get (Line, Pointer, SpaceAndTab); Get (Line, Pointer, Flag); Get (Line, Pointer, SpaceAndTab); Valid := Valid and then Flag >= 1; end loop; if Pointer <= Line'Last then Put_Line ("Unrecognized tail at " & Image (Line_No) & ':' & Image (Pointer)); elsif Valid then Count := Count + 1; end if; exception when End_Error | Data_Error | Constraint_Error | Time_Error => Put_Line ("Syntax error at " & Image (Line_No) & ':' & Image (Pointer)); end; end loop;
exception
when End_Error => Close (File); Put_Line ("Valid records " & Image (Count) & " of " & Image (Line_No) & " total");
end Data_Munging_2; </ada> Sample output
1990-3-25: record at 85 duplicates record at 84 1991-3-31: record at 456 duplicates record at 455 1992-3-29: record at 820 duplicates record at 819 1993-3-28: record at 1184 duplicates record at 1183 1995-3-26: record at 1911 duplicates record at 1910 Valid records 5017 of 5471 total
AWK
A series of AWK one-liners are shown as this is often what is done. If this information were needed repeatedly, (and this is not known), a more permanent shell script might be created that combined multi-line versions of the scripts below.
Gradually tie down the format.
(In each case offending lines will be printed)
If their are any scientific notation fields then their will be an e in the file:
bash$ awk '/[eE]/' readings.txt bash$
Quick check on the number of fields:
bash$ awk 'NF != 49' readings.txt bash$
Full check on the file format using a regular expression:
bash$ awk '!(/^[0-9][0-9][0-9][0-9]-[0-9][0-9]-[0-9][0-9]([ \t]+[-]?[0-9]+\.[0-9]+[\t ]+[-]?[0-9]+)+$/ && NF==49)' readings.txt bash$
Full check on the file format as above but using regular expressions allowing intervals (gnu awk):
bash$ awk --re-interval '!(/^[0-9]{4}-[0-9]{2}-[0-9]{2}([ \t]+[-]?[0-9]+\.[0-9]+[\t ]+[-]?[0-9]+){24}+$/ )' readings.txt bash$
Identify any DATASTAMPs that are duplicated.
Accomplished by counting how many times the first field occurs and noting any second occurrences.
bash$ awk '++count[$1]==2{print $1}' readings.txt 1990-03-25 1991-03-31 1992-03-29 1993-03-28 1995-03-26 bash$
What number of records have good readings for all instruments.
bash$ awk '{rec++;ok=1; for(i=0;i<24;i++){if($(2*i+3)<1){ok=0}}; recordok += ok} END {print "Total records",rec,"OK records", recordok, "or", recordok/rec*100,"%"}' readings.txt Total records 5471 OK records 5017 or 91.7017 % bash$
OCaml
<ocaml>#load "str.cma" open Str
let strip_cr str =
let last = pred(String.length str) in if str.[last] <> '\r' then (str) else (String.sub str 0 last)
let map_records =
let rec aux acc = function | value::flag::tail -> let e = (float_of_string value, int_of_string flag) in aux (e::acc) tail | _::[] -> invalid_arg "invalid data" | [] -> (List.rev acc) in aux [] ;;
let duplicated_dates =
let same_date (d1,_) (d2,_) = (d1 = d2) in let date (d,_) = d in let rec aux acc = function | a::b::tl when same_date a b -> aux (date a::acc) tl | _::tl -> aux acc tl | [] -> (List.rev acc) in aux [] ;;
let record_ok (_,record) =
let is_ok (_,v) = (v >= 1) in let sum_ok = List.fold_left (fun sum this -> if is_ok this then succ sum else sum) 0 record in (sum_ok = 24)
let num_good_records =
List.fold_left (fun sum record -> if record_ok record then succ sum else sum) 0 ;;
let parse_line line =
let li = split (regexp "[ \t]+") line in let records = map_records (List.tl li) and date = (List.hd li) in (date, records)
let () =
let ic = open_in "readings.txt" in let rec read_loop acc = try let line = strip_cr(input_line ic) in read_loop ((parse_line line) :: acc) with End_of_file -> close_in ic; (List.rev acc) in let inputs = read_loop [] in
Printf.printf "%d total lines\n" (List.length inputs);
Printf.printf "duplicated dates:\n"; let dups = duplicated_dates inputs in List.iter print_endline dups;
Printf.printf "number of good records: %d\n" (num_good_records inputs);
- </ocaml>
this script outputs:
5471 total lines duplicated dates: 1990-03-25 1991-03-31 1992-03-29 1993-03-28 1995-03-26 number of good records: 5017
Perl
<perl>use List::MoreUtils 'natatime'; use constant FIELDS => 49;
binmode STDIN, ':crlf';
# Read the newlines properly even if we're not running on # Windows.
my ($line, $good_records, %dates) = (0, 0); while (<>)
{++$line; my @fs = split /\s+/; @fs == FIELDS or die "$line: Bad number of fields.\n"; for (shift @fs) {/\d{4}-\d{2}-\d{2}/ or die "$line: Bad date format.\n"; ++$dates{$_};} my $iterator = natatime 2, @fs; my $all_flags_okay = 1; while ( my ($val, $flag) = $iterator->() ) {$val =~ /\d+\.\d+/ or die "$line: Bad value format.\n"; $flag =~ /\A-?\d+/ or die "$line: Bad flag format.\n"; $flag < 1 and $all_flags_okay = 0;} $all_flags_okay and ++$good_records;}
print "Good records: $good_records\n",
"Repeated timestamps:\n", map {" $_\n"} grep {$dates{$_} > 1} sort keys %dates;</perl>
Output:
Good records: 5017 Repeated timestamps: 1990-03-25 1991-03-31 1992-03-29 1993-03-28 1995-03-26
Python
<Python>import re import zipfile import StringIO
def munge2(readings):
datePat = re.compile(r'\d{4}-\d{2}-\d{2}') valuPat = re.compile(r'[-+]?\d+\.\d+') statPat = re.compile(r'-?\d+') allOk, totalLines = 0, 0 datestamps = set([]) for line in readings: totalLines += 1 fields = line.split('\t') date = fields[0] pairs = [(fields[i],fields[i+1]) for i in range(1,len(fields),2)]
lineFormatOk = datePat.match(date) and \ all( valuPat.match(p[0]) for p in pairs ) and \ all( statPat.match(p[1]) for p in pairs ) if not lineFormatOk: print 'Bad formatting', line continue
if len(pairs)!=24 or any( int(p[1]) < 1 for p in pairs ): print 'Missing values', line continue
if date in datestamps: print 'Duplicate datestamp', line continue datestamps.add(date) allOk += 1
print 'Lines with all readings: ', allOk print 'Total records: ', totalLines
- zfs = zipfile.ZipFile('readings.zip','r')
- readings = StringIO.StringIO(zfs.read('readings.txt'))
readings = open('readings.txt','r') munge2(readings)</Python> The results indicate 5013 good records, which differs from the Awk implementation. The final few lines of the output are as follows
Missing values 2004-12-29 2.900 1 2.700 1 2.800 1 3.300 1 2.900 1 2.300 1 0.000 0 1.700 1 1.900 1 2.300 1 2.600 1 2.900 1 2.600 1 2.600 1 2.600 1 2.700 1 2.300 1 2.200 1 2.100 1 2.000 1 2.100 1 2.100 1 2.300 1 2.400 1 Missing values 2004-12-30 2.400 1 2.600 1 2.600 1 2.600 1 3.000 1 0.000 0 3.300 1 2.600 1 2.900 1 2.400 1 2.300 1 2.900 1 3.500 1 3.700 1 3.600 1 4.000 1 3.400 1 2.400 1 2.500 1 2.600 1 2.600 1 2.800 1 2.400 1 2.200 1 Missing values 2004-12-31 2.400 1 2.500 1 2.500 1 2.400 1 0.000 0 2.400 1 2.400 1 2.400 1 2.200 1 2.400 1 2.500 1 2.000 1 1.700 1 1.400 1 1.500 1 1.900 1 1.700 1 2.000 1 2.000 1 2.200 1 1.700 1 1.500 1 1.800 1 1.800 1 Lines with all readings: 5013 Total records: 5471
Second Version
Modification of the version above to:
- Remove continue statements so it counts as the AWK example does.
- Generate mostly summary information that is easier to compare to other solutions.
<python>import re import zipfile import StringIO
def munge2(readings, debug=False):
datePat = re.compile(r'\d{4}-\d{2}-\d{2}') valuPat = re.compile(r'[-+]?\d+\.\d+') statPat = re.compile(r'-?\d+') totalLines = 0 dupdate, badform, badlen, badreading = set(), set(), set(), 0 datestamps = set([]) for line in readings: totalLines += 1 fields = line.split('\t') date = fields[0] pairs = [(fields[i],fields[i+1]) for i in range(1,len(fields),2)] lineFormatOk = datePat.match(date) and \ all( valuPat.match(p[0]) for p in pairs ) and \ all( statPat.match(p[1]) for p in pairs ) if not lineFormatOk: if debug: print 'Bad formatting', line badform.add(date) if len(pairs)!=24 or any( int(p[1]) < 1 for p in pairs ): if debug: print 'Missing values', line if len(pairs)!=24: badlen.add(date) if any( int(p[1]) < 1 for p in pairs ): badreading += 1 if date in datestamps: if debug: print 'Duplicate datestamp', line dupdate.add(date)
datestamps.add(date)
print 'Duplicate dates:\n ', '\n '.join(sorted(dupdate)) print 'Bad format:\n ', '\n '.join(sorted(badform)) print 'Bad number of fields:\n ', '\n '.join(sorted(badlen)) print 'Records with good readings: %i = %5.2f%%\n' % ( totalLines-badreading, (totalLines-badreading)/float(totalLines)*100 ) print 'Total records: ', totalLines
readings = open('readings.txt','r') munge2(readings) </python>
bash$ /cygdrive/c/Python26/python munge2.py Duplicate dates: 1990-03-25 1991-03-31 1992-03-29 1993-03-28 1995-03-26 Bad format: Bad number of fields: Records with good readings: 5017 = 91.70% Total records: 5471 bash$
Tcl
set data [lrange [split [read [open "readings.txt" "r"]] "\n"] 0 end-1] set total [llength $data] set correct $total set datestamps {} foreach line $data { set formatOk true set hasAllMeasurements true set date [lindex $line 0] if {[llength $line] != 49} { set formatOk false } if {![regexp {\d{4}-\d{2}-\d{2}} $date]} { set formatOk false } if {[lsearch $datestamps $date] != -1} { puts "Duplicate datestamp: $date" } {lappend datestamps $date} foreach {value flag} [lrange $line 1 end] { if {$flag < 1} { set hasAllMeasurements false } if {![regexp -- {[-+]?\d+\.\d+} $value] || ![regexp -- {-?\d+} $flag]} {set formatOk false} } if {!$hasAllMeasurements} { incr correct -1 } if {!$formatOk} { puts "line \"$line\" has wrong format" } } puts "$correct records with good readings = [expr $correct * 100.0 / $total]%" puts "Total records: $total"
$ tclsh munge2.tcl Duplicate datestamp: 1990-03-25 Duplicate datestamp: 1991-03-31 Duplicate datestamp: 1992-03-29 Duplicate datestamp: 1993-03-28 Duplicate datestamp: 1995-03-26 5017 records with good readings = 91.7016998721% Total records: 5471