How can I calculate the depreciated value based on the previous value?

[Tomo230485]

Hi,

I am new to SAS and I was hoping I could get some help in this forum.

I would like to know how I can calculate the depreciated/appreciated value based on the value avaiable within each group.

So if I have the following table, 

data test;
input id km sale dep_rate;
datalines;
1 10000 0 -0.05
1 20000 0 -0.05
1 30000 200 -0.05
1 40000 0 -0.05
1 50000 0 -0.05
1 60000 0 -0.05
2 10000 0 -0.02
2 20000 0 -0.02
2 30000 500 -0.02
2 40000 0 -0.02
2 50000 0 -0.02
2 60000 0 -0.02
3 10000 0 -0.03
3 20000 0 -0.03
3 30000 300 -0.03
3 40000 0 -0.03
3 50000 0 -0.03
;
run;

I would like to know how to achive the following result.

It calculates the depreciated/appreicated value of each group based on it's depreciation rate and each km group. 

ID	KM	SALE	DEP_RATE	OUTCOME
1	10000	0	-0.05	220.50
1	20000	0	-0.05	210.00
1	30000	200	-0.05	200.00
1	40000	0	-0.05	190.00
1	50000	0	-0.05	180.50
1	60000	0	-0.05	171.48
2	10000	0	-0.02	520.20
2	20000	0	-0.02	510.00
2	30000	500	-0.02	500.00
2	40000	0	-0.02	490.00
2	50000	0	-0.02	480.20
2	60000	0	-0.02	470.60
3	10000	0	-0.03	318.27
3	20000	0	-0.03	309.00
3	30000	300	-0.03	300.00
3	40000	0	-0.03	291.00
3	50000	0	-0.03	282.27

I have a feeling that I need to use retain, loop and lag to find depreciated value first, then sort the other way around to find appreciated value.

Finally use the value from depreicated or appreciated variable as RESULT.

However, I can not figure out how I should utilise those functions to achive my result.....

Any advice would be much appreciated.

Tom

[RahulG]

I think there is something missing.

How would I know the base value of vehicle at 0 KM?

I have added a row for every id- sale value of vehicle at 0 km

data test;
input id km sale dep_rate;
datalines;
1 0 230 0
1 10000 0 -0.05
1 20000 0 -0.05
1 30000 200 -0.05
1 40000 0 -0.05
1 50000 0 -0.05
1 60000 0 -0.05
2 0 500 0
2 10000 0 -0.02
2 20000 0 -0.02
2 30000 500 -0.02
2 40000 0 -0.02
2 50000 0 -0.02
2 60000 0 -0.02
3 0 400 0
3 10000 0 -0.03
3 20000 0 -0.03
3 30000 300 -0.03
3 40000 0 -0.03
3 50000 0 -0.03
;
run;

data output(drop = last_sale_value);
retain last_sale_value;
set test;
by id;
if first.id then do;
last_sale_value=sale;
outcome=sale;
end;
else do;
if sale > 0 then outcome=sale;
else outcome=round(last_sale_value*sum(1,dep_rate),0.01);
last_sale_value=outcome;
end;
run;

[Tomo230485]

Thank you for your quick reply!
It sort of works but the outcome for the appreciated value seems to be wrong. I guess that is due to relying on the base value you created?
ID:1 KM:20,000 outcome should be 210 (200 * 0.05 + 200).
However your outcomes shows 207.58.

[Ksharp · Accepted solution]

Hmm. Interesting .

data test;
input id km sale dep_rate;
datalines;
1 10000 0 -0.05
1 20000 0 -0.05
1 30000 200 -0.05
1 40000 0 -0.05
1 50000 0 -0.05
1 60000 0 -0.05
2 10000 0 -0.02
2 20000 0 -0.02
2 30000 500 -0.02
2 40000 0 -0.02
2 50000 0 -0.02
2 60000 0 -0.02
3 10000 0 -0.03
3 20000 0 -0.03
3 30000 300 -0.03
3 40000 0 -0.03
3 50000 0 -0.03
;
run;
data temp key(keep=id n sale  rename=(n=_n sale=_sale));
 set test;
 by id;
 if first.id then n=0;
 n+1;
 if sale ne 0 then output key;
 output temp;
run;
data want;
 merge temp key;
 by id;
 period=n-_n;
 OUTCOME=_sale*(1+dep_rate)**period;
 drop _: n period;
run;

[Tomo230485]

Smart and Simple way!
I was thinking of it in very complicated way.
Thank you!

[RahulG]

Indeed very smart.