Date:         Sun, 30 Apr 2006 22:49:46 -0400
Reply-To:     "Howard Schreier <hs AT dc-sug DOT org>" <nospam@HOWLES.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         "Howard Schreier <hs AT dc-sug DOT org>" <nospam@HOWLES.COM>
Subject:      Re: Lifecycle Analysis: Depreciate Assets into the Future?

On Wed, 26 Apr 2006 18:23:11 -0400, Peter Larsen <phlarsen@YAHOO.COM>
wrote:

>Hi Folks-
>
>BACKGROUND: I am building a program that contains different types of
>public infrastructure that have various lifespans (e.g. 10 and 15 years in
>my example below).  Ideally, I would like to see the value of these assets
>depreciate over time based on the lifespan identified in the dataset.
>
>In the future (i.e. Year_2007, Year_2020, etc.), if the value of the asset
>hits (or goes below) zero, I want to have SAS replace that depreciated
>value with the original value (i.e. ReplValue) AND begin the depreciation
>process all over again until the program reaches the date identified in
>the %let statement (i.e. FUTURE).  Finally, I would like to calculate the
>present value of what it would cost in today's dollars to replace the
>piece of infrastructure as many times as necessary given the lifespan of
>the asset and FUTURE date identified in the %let statement.
>
>QUESTION: How do I go about doing all of this assuming that:
>A) The rate of depreciation could be linear OR could be exponential with
>both types of decay based on the lifespan of the asset.  For example, an
>asset with a 10 year lifespan decayed linearly would show the asset
>decreasing 10% per year until it reaches zero in 2016.  NOTE: For reasons
>I don't want to get into now, it is entirely plausible that the
>exponential decay would occur in addition to the linear decay.  So, in
>short, I would like to see two sets of present value results: one just
>linear and the other an exponential decay in addition to the linear decay
>over time.  Make sense?
>
>B) The interest rate used is the PV calculation is fixed.
>
>As usual, many thanks for your help in advance.  I assume this is some
>sort of nested "do" loop statement, but I can't figure it out just yet.

Show your code, and the results, and explain the deficiencies.

>
>Pete
>
>----------------------
>options  macrogen    mlogic    source    source2    symbolgen   sortsize =
>80M;
>
>TITLE1 'INFRASTRUCTURE DATABASE';
>DATA INFRA;
>     INPUT Location $ Type $ ReplValue YearBuilt LifeSpan;
>     CARDS;
>   Bethel School 10000 2006 10
> Nome School 20000 1960 15
>;
>run;
>
>%macro generic;
>
>%let FUTURE = 2026;
>%let INTRATE=0.07;
>
>data Infra;
> set Infra;
> format ReplValue dollar20.;
> informat ReplValue dollar20.;
>  %do i=2006 %to &FUTURE.;
>   Year_&i.=ReplValue;
>   format Year_&i. dollar20.;
>   informat Year_&i. dollar20.;
>  %end;

The DATA step has array and looping features. It's not necessary to use
macro code to control repetitious processes.

>run;
>
>%mend generic;
>%generic;