Bash – Leap year – extrapolating value

bashshelltable

I have some tables (table.txt) as follow:

YEAR MONTH DAY RES
1971 1     1   1345
1971 1     2   1265
1971 1     3   1167

The length of each time series goes from 1.1.1971 until 31.12.2099. Unfortunately, some time series are missing leap years and their values (e.g. year 1972 is a leap year so the month of February should have 29 days, but my time series just have 28 days in February 1972). For examples in my current tables the end of the February month in 1972 is presented as follow:

YEAR MONTH DAY RES
1972 2     27  100
1972 2     28  101
1972 3     1   102

This is wrong, cause it´s not accounting any leap year. Instead of that I would like to include in my time series each missing days (obviously the 29th of February) of every leap years in my time series, by extrapolating the value with the previous and next day, as follow:

YEAR MONTH DAY RES
1972 2     27  100
1972 2     28  101
1972 2     29  101.5
1972 3     1   102

Is there a way to do that using shell/bash?

Best Answer

Maybe something like:

awk '
  function isleap(y) {
    return y % 4 == 0 && (y % 100 != 0 || y % 400 == 0)
  }
  $2 == 3 && $3 == 1 && isleap($1) && last_day != 29 {
    print $1, 2, 29, (last_data + $4) / 2
  }
  {print; last_day = $3; last_data = $4}' file

Related Solutions

Shell – Delete files based on year

Most filesystems don't store the creation time of a file, so the best you can do is check the last time the file was modified.

If you have a recent version of GNU find (e.g. on Linux or Cygwin) or FreeBSD or OSX, you can directly compare the date of a file with that of another file. In addition, these versions of find can use the file creation time (called its birth time, indicated with a B) if it's available on your system. Replace B by m below to use the modification time rather than the birth time.

find /path/to/directory -newerBt '2009-01-01' ! -newerBt '2010-01-01' -type f -delete

Run it once without -delete first to make sure these are the files you want. The command above will also delete files in subdirectories; if this is not desired, add -mindepth 1 -maxdepth 1 after the directory name.

If your version of find doesn't have the -newerXY primary, you'll need to create timestamp files to mark the boundaries of the range of times you want to match.

touch -t 200901010000 /tmp/from
touch -t 201001010000 /tmp/to
find /path/to/directory -newer /tmp/from ! -newer /tmp/to -type f -exec rm {} +

Zsh's glob qualifiers can match files in a time interval, but the boundaries can only be indicated relative to the current date (e.g. N days ago).

rm /path/to/directory/*(.m+566^m+931)

You can also use timestamp files for precise dates, but you lose in terseness.

touch -t 200901010000 /tmp/from
touch -t 201001010000 /tmp/to
rm /path/to/directory/*(.e\''[[ $REPLY -nt /tmp/from && $REPLY -ot /tmp/to ]]'\')

Bash – What does : ${param:=value} mean

Let's break this down into pieces.

This code runs the command : with some arguments. The command : does nothing and ignores its arguments. Therefore the whole command line does nothing, except whatever side effects happen in the arguments.

The syntax ${parameter_name:=value} exists in all non-antique Bourne-style shells, including ash, bash, ksh and zsh. It sets the parameter to a default if necessary. It is equivalent to

if [ -z "$parameter_name" ]; then parameter_name=value; fi
… ${parameter_name}

In other words, if parameter_name is not set or is set to an empty value, then set it to the indicated value; and then run the command, using the new parameter value. There is a variant, ${parameter_name=value}, which leaves the parameter empty if it was empty, only using the indicated value if the parameter was unset.

You'll find this syntax documented under “parameter expansion” in the POSIX spec, and the dash, bash, ksh and zsh manuals.

There are variations on this syntax, in particular ${parameter_name:-value} which let you use a default value for this expansion only, without assigning to the parameter.

In summary, : ${parameter_name:=value} is a concise way of writing

if [ -z "$parameter_name" ]; then parameter_name=value; fi

Best Answer

Related Solutions

Shell – Delete files based on year

Bash – What does : ${param:=value} mean

Related Question