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Hi Roberto,
No other replies to your Q yet, so it is my turn [;-)
For TN (or _N_) = 1 you already indicate DPC and DCQ to be missing. So in that case CTi would be missing as well. That means that CTAi would be missing for TN=1 too and while all subsequent CTAi's would be accumulated from CTAi for TN=1, they all would be missing. I assume that you want all non-missing sums, so I have developed the following code:
DATA LoopTest;
INPUT TN PC CQ;
DPC=PC-LAG1(PC);
DCQ=CQ-LAG1(CQ);
CTi=dpc*dcq/2;
RETAIN CTAi;
IF (_N_ /* or TN */ EQ 1) THEN CTAi = CTi; * thus missing for TN=1;
ELSE CTAi = SUM ( CTi, CTAi );
* Even without the IF/ELSE the last assignment could apply always, also for TN=1;
CARDS;
1 25 245
2 50 543
3 75 645
4 100 725
5 125 876
6 150 965
7 175 1145
8 200 1178
9 225 1178
10 250 1178
;
RUN;
PROC PRINT DATA = LoopTest; RUN;
Regards - Jim.
Y. (Jim) Groeneveld MSc
Biostatistician
Vitatron B.V.
Meander 1051
6825 MJ Arnhem
The Netherlands
+31/0 26 376 7365; fax 7305
Jim.Groeneveld@Vitatron.com
www.vitatron.com
-----Original Message-----
From: Roberto Valdivia [mailto:valdivia@MONTANA.EDU]
Sent: Thursday, September 04, 2003 23:13
To: SAS-L@LISTSERV.UGA.EDU
Subject: Help with a loop!
Importance: High
Hi!, I have a problem writting a code to make an analysis, it might be
simple to solve,
but unfortunately, I couldn't get it right. So, please, could anyone help me
with this?.
Below is the problem described,
Thanks in advance,
Roberto.
I have a data like this:
tn pc cq
1 25 245
2 50 543
3 75 645
4 100 725
5 125 876
6 150 965
7 175 1145
8 200 1178
9 225 1178
10 250 1178
First I need to estimate the difference between PCi - PCi-1 (where i=tn,
i.e. when TN=2 and when TN=1 => 50-25=25),
I did this using the "lag" command :
DPC=PC-LAG1(PC); Same thing for the CQ variable:
DCQ=CQ-LAG1(CQ);
Now I have these two variables in the dataset (note that the first
observation is missing for DPC and DCQ):
tn pc cq dpc dcq
1 25 245 . .
2 50 543 25 298
3 75 645 25 102
4 100 725 25 80
5 125 876 25 151
6 150 965 25 89
7 175 1145 25 180
8 200 1178 25 33
9 225 1178 25 0
10 250 1178 25 0
Here is my question:
I need to estimate a value like CTi=dpc*dcq/2 (i is the observation number).
After this, I need to have a variable that accumulate this value
each "tn", so for example: If "i" is the index for TN (observation number)
for TN=1 CTAi=CTi
for TN=2 CTAi=CTi + CTi-1
for TN=3 CTAi=CTi + CTi-1 +CTi-2
OR, IN GENERAL: CTAi=CTi+CTAi-1
I've tried to do this using the DO statement to build a loop but I cannot
get it work.
Any help will be appreciated.
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