Delila Program: logscale

logscale program

Documentation for the logscale program is below, with links to related programs in the "see also" section.

{   version = 1.02; (* of logscale.p 2010 Sep 18}

(* begin module describe.logscale *)
(*
name
   logscale: provide numbers on a log scale

synopsis
   logscale(input: in, output: out)

files

   input: one line with the following values:

      x (real): starting value
      b (integer): base of the scale (eg 2 or 10)
      n (integer): number of intervals
        If n is negative, report the program version number.
      m (integer): which interval we are on
      w (integer): width of output number (characters)
      d (integer): decimal places of output number (characters)

   output: messages to the user

description

   Create numbers on a log scale one at a time for use in scripts.

Let the scale look like this (where b = 10):

   x * z * z * z * z = 10x

   So here x is the starting value.  It is successively multiplied by z
   n = 4 times until we reach 10x.

   So for

   m = 0  result = x
   m = 1  result = x * z
   m = 2  result = x * z * z
   m = 3  result = x * z * z * z
   m = 4  result = x * z * z * z * z

   So now all we need to know is the value of z.

   From the first equation,

   z^n = b

   so

   z = b ^ (1/n)

   then:

   result = x * z^m

examples

The tcsh script:

set m = 0
while ($m < 13)
   # x (real): starting value
   # b (integer): base of the scale (eg 2 or 10)
   # n (integer): number of intervals
   # m (integer): which interval we are on
   # w (integer): width of output number (characters)
   # d (integer): decimal places of output number (characters)
   printf "%2d " $m
   #     x b n  m w d
   echo "1 2 4 $m 4 2" | logscale
   @ m = $m + 1
end

gives:

 0 1.00
 1 1.19
 2 1.41
 3 1.68
 4 2.00
 5 2.38
 6 2.83
 7 3.36
 8 4.00
 9 4.76
10 5.66
11 6.73
12 8.00

   output: messages to the user

description

   Create numbers on a log scale one at a time for use in scripts.

Let the scale look like this (where b = 10):

   x * z * z * z * z = 10x

   So here x is the starting value.  It is successively multiplied by z
   n = 4 times until we reach 10x.

   So for

   m = 0  result = x
   m = 1  result = x * z
   m = 2  result = x * z * z
   m = 3  result = x * z * z * z
   m = 4  result = x * z * z * z * z

   So now all we need to know is the value of z.

   From the first equation,

   z^n = b

   so

   z = b ^ (1/n)

   then:

   result = x * z^m

examples
   echo "

documentation


documentation

see also

author

   Thomas Dana Schneider

bugs

technical notes

*)
(* end module describe.logscale *)
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