Is there a shell scrior Perl script to calculate Relative Humidity(%) using T_DB(Temp - Dry Bulb) and DP ( Dew Point)?

Question

All I have is this

Tc=air temperature in degrees Celsius

Tdc=dewpoint temperature in degrees Celsius

(1) Es=6.11*10.0** (7.5*Tc/ (237.7+Tc))

(2) E=6.11*10.0** (7.5*Tdc/ (237.7+Tdc))

(3) Relative Humidity (RH) in percent = (E/Es)*100

In fact ( froma CSV file ) I need to grab a value from Column9 and one from Col 10 use those values to calculate Relative Humidity(%) and put the result at the end of the record/ line. This needs to be repeated till the end of the csv file.

Any help appreciated

cheers

Answer 1

Put the following code in calc_rh.pl:

#!/usr/bin/perl

while (<>) {
    chomp;
    @f = map { /^\"(.*)\"$/ ? $1 : $_ } split /,/;   # Strips double quotes if present
    ($Tc, $Tdc) = @f[8, 9];       # Assuming Tc in column 9, Tdc in column 10
    $Es=6.11*10.0** (7.5*$Tc/ (237.7+$Tc));
    $E=6.11*10.0** (7.5*$Tdc/ (237.7+$Tdc));
    $RH = sprintf "%.2f", $E/$Es*100;    # Or use e.g. "%.4f" for 4 digits after d.p.
    print join(",", map { "\"$_\"" } @f, $RH), "\n";
}

Run with:

perl calc_rh.pl < infile.csv > outfile.csv

NOTE: The code above will break if any of your columns contain a comma. It's possible to fix this using downloadable modules, but I get the feeling you just need a quick script.

Also, if you're running in Linux, you may need to run:

perl ./calc_rh.pl < infile.csv > outfile.csv

instead.

Answer 2

Guru....thanks mate I think its working ...

cheers