Shell Programming and Scripting

i have a column of numbers and i need to find the percentage drops or increases from line to line.

suppose i have this:

Code:

45
14
14
2
8
8
8

the output im currently getting is this:

Code:

14
14,0%
2
8,75%
8
8,0%

which was produced by the following code:

Code:

awk '{prev=$1; print; getline; print $0","($1-prev)/$1*100"%"}'

the problem is when one of the numbers is a zero, awk bombs out. is there a way to modify this awk code to check to see if the numbers are zero, and if zero, it'll just assume a 0% change?

i basically have specific values for 24 hours. and i need to print the percentage drop or increase from hour to hour.

so lets assume the last 4 hours have the value:

20:00,120
21:00,50
22:00,39
23:00,90
00:00,70

the code im looking for will produce the following output:

Code:

20:00,120,-80%
21:00,50,-15%
22:00,39,-34%
23:00,90,+69%
00:00,70,-20%

note, the percentages above are wrong. i just put them there as an example.

but what im trying to do here is calculate the percentage drop or increases from one hour to the next.

i apologize if i inadvertently made this complicated.

Something along this line:

Code:

awk -F, '
NR > 1  {if ($2 !=0)    {TMP = ($2 - PREV) / $2 * 100
                         $3 = sprintf ("%.2f %%", TMP)
                        }
         else $3 = "zero value"
        }
        {PREV = $2
        }
1
' OFS=, file
20:00,120
21:00,50,-140.00 %
22:00,39,-28.21 %
23:00,90,56.67 %
00:00,70,-28.57 %