[R] Formula that includes previous row values
Pele
drdionc at yahoo.com
Mon Feb 23 21:59:18 CET 2009
Hi R users,
Is there an easy way in R to generate the results table below using table 1
and the formula (simplified version of the real problem)? It would be easy
if I knew the R equivalent of SAS's retain function, but could not find one.
Thanks in Advance for any help!
table1:
ID X2 X3
1.00 1.00 0
2.00 0.00
3.00 1.00
4.00 3058
5.00 0.00
6.00 6.00
Formula: X3 = x2 + (.24 * x3)
where the values in the x3 column of the result table are retained from
previous x3 rows.. Also the first x3 value is initialized to 0 to start
e.g.
for ID=1 we have 1 + .24(0) = 1.00
for ID=2 we have 0 + .24(1) = 0.24
for ID=3 we have 1 + .24(.24) = 1.06
for ID=4 we have 3058 + .24(1.06) = 3058.25
etc.............
Results:
ID X2 x3
1.00 1.00 1.00
2.00 0.00 0.24
3.00 1.00 1.06
4.00 3058 3058.25
5.00 0.00 733.98
6.00 6.00 182.16
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