in reply to Re: BASIC MATH WITH DATA
in thread BASIC MATH WITH DATA

Just a little more Help here..... and I think it will work. I added some stuff to make the script load a file and output a log file. However there is some error in the script that I cannot resolve. Could someone please have a look....?? while we are editing the $text line..... could you also include the value of the most resent value entered in col3 
#!/usr/bin/perl -w
       $infile = shift;
       $outfile = shift;
       
       open(IN, $infile) || die("Can't open input file $infile - $!");
       open(OUT, ">$outfile") || die("Can't open output file $outfile 
+- $!");

       use strict;
       my $text;
       my @lines;

       while (<>) {
         push @lines;
         shift @lines if @lines > 10;
       }

       chomp(@lines);

       my @cols;
       my $total = 0;

       for (@lines) {
         @cols = split /:/;
         $total += $cols[3];
       }
       my $average = $total / (@lines || 1);
         # if no lines, avoid division by zero

       
 ***** error here*****      $text= "Average of column 3 for the last "
+ ;#, scalar(@lines)," days: $average\n";
       


      print OUT "$text\n";
    
       close IN;
       close OUT ;

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So the message in the Data.log file would read "<Filename> Average is <average> the last was <most resent entry for col3>" Thank you.. this has been good experience..... wish something like this was in the book I bought. joachim

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Re: Re: Re: BASIC MATH WITH DATA
by chipmunk (Parson) on Jan 26, 2001 at 01:55 UTC
    Quote: 
      $text= "Average of column 3 for the last " ;
             #, scalar (@lines)," days: $average\n";

    [download]
    Originally, that was a print statement, in which the commas were fine. With a scalar assignment, the commas should be replaced with concatenation: 
    $text = "Average of column 3 for the last " .
              scalar(@lines) . " days: $average\n";

    [download]
    or with join: 
    $text = join '', "Average of column 3 for the last ",
                       scalar(@lines), " days: $average\n";

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    or with a single interpolated string, or with sprintf... There's more than one way to do it.
     

    The last line is at @lines[-1]; one way to get the most recent value is: my $last = (split /:/, $lines[-1])[3]; The ( )[3] is called a list slice. It's basically a short way of doing: 

    my @tmp = split /:/, $lines[-1];
my $last = $tmp[3];

    [download]
    Instead of assigning to the array @tmp and then looking up index 3, the list slice just does the index directly on the list. They give the same results, though, so use whichever is clearer.
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      OK....This is almost there..... thanks for the <IN> tip.... it looked like a small correction... it's gotta be in there... thanks 
      
#!/usr/bin/perl -w
       $infile = shift;
       $outfile = shift;
       
       open(IN, $infile) || die("Can't open input file $infile - $!");
       open(OUT, ">$outfile") || die("Can't open output file $outfile 
+- $!");

       use strict;
       my $text;
       my @lines;
       

#my @tmp = split /:/, $lines[-1];   these two go together
#my $last = $tmp[3];                 as an alternate way of doing this
+ routine
#                                    learn this in next attempt
     
       while (<IN>) {
         push @lines;
         shift @lines if @lines > 10;
       }

       chomp(@lines);

       my @cols;
       my $total = 0;

       for (@lines) {
         @cols = split /:/;
         $total += $cols[3];
       }
       my $average = $total / (@lines || 1);
         # if no lines, avoid division by zero

       my $last = (split /:/, $lines[-1])[3];

 $text = "Average of column 3 for the last " .
                              scalar(@lines) . " days: $average\n";   
+    
  $last ="Last value in Col3" . scalar(@lines) . " value: $last\n";

      print OUT "$text\n";
      print OUT "$last\n";

    
       close IN;
       close OUT ;
  
   
<\code>
 The message in the log file reads.....

<code>

Average of column 3 for the last 0 days: 0

Last value in Col30 value:

      [download]
      Lights are flashing on my machine.... files are poping on the screen.... this is good.... but what am I missing .... all the values read "0" I have run this script through the Perl Builder debugger and it does not indicate errors...which is too bad. There are obviously still some errors in here. Would someone please have a look.... Thanks Joachim
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[d/l]

        If you are comfortable using the debugger, now would be a good time to fire it up: "perl -d script.pl". If you aren't comfortable, then you might consider this as a good time to get comfortable. (: Otherwise, I suggest you get more data. Data::Dumper is great for this, but you could start with just a: 

        print "($cols[3]) $_";

        [download]
        just above the $total += $cols[3]; line.

                - tye (but my friends call me "Tye")
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Re^3: Basic math with Data
by lemming (Priest) on Jan 26, 2001 at 01:59 UTC
    You might want to read from your IN file.
    Try <IN> instead of just <>.

    Editorial: Instead of just cut and pasting chipmunk's code, try to understand what it does. Pick up Learning Perl, browse the other book reviews & purchase other worthy recommended books

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      OK....This is almost there..... thanks for the "IN" tip.... it looked like a small correction... it's gotta be in there. .... thanks ... only one small problem... it's not doing the "OUTPUT" unfortunately.... please have a look..... 
      
#!/usr/bin/perl -w
       $infile = shift;
       $outfile = shift;
       
       open(IN, $infile) || die("Can't open input file $infile - $!");
       open(OUT, ">$outfile") || die("Can't open output file $outfile 
+- $!");

       use strict;
       my $text;
       my @lines;
       

#my @tmp = split /:/, $lines[-1];   these two go together
#my $last = $tmp[3];                 as an alternate way of doing this
+ routine
#                                    learn this in next attempt
     
       while (<IN>) {
         push @lines;
         shift @lines if @lines > 10;
       }

       chomp(@lines);

       my @cols;
       my $total = 0;

       for (@lines) {
         @cols = split /:/;
         $total += $cols[3];
       }
       my $average = $total / (@lines || 1);
         # if no lines, avoid division by zero

       my $last = (split /:/, $lines[-1])[3];

 $text = "Average of column 3 for the last " .
                              scalar(@lines) . " days: $average\n";   
+    
  $last ="Last value in Col3" . scalar(@lines) . " value: $last\n";

      print OUT "$text\n";
      print OUT "$last\n";

    
       close IN;
       close OUT ;
  
   
<\code>
 The message in the log file reads.....

<code>

Average of column 3 for the last 0 days: 0

Last value in Col30 value:

      [download]
      Lights are flashing on my machine.... files are poping on the screen.... this is good.... but what am I missing .... all the values read "0" or are " " blank I have run this script through the Perl Builder debugger and it does not indicate errors...which is too bad. There are obviously still some errors in here. Would someone please have a look.... Thanks Joachim
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[select]
        This is my fault. The line: push @rows; should be: push @rows, $_; I always forget that $_ is not the default argument for push.

        I've updated the original code to correct my error.

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