On 30/05/17 19:02, Vijaya Kumar Regati wrote:
Hi,
I am new to R programming, I am trying to work on below requirement. But could
not achieve desired result.
Appreciate if someone can help me on this :
test dataframe :
Day1.balc Day2.balc Day3.balc Day4.balc
x 100 20 30 40
y 100 10 10 10
class(test)
[1] "data.frame"
My Goal is to accomplish :
Day2.balc <- Day2.balc + Day1.balc
Day3.balc <- Day3.balc + Day2.balc
.
.
.
Day30.balc <- Day30.balc + Day29.balc
# Testing for first 4 days
for (i in 1:4 ) {
test$Day[i].balc <- test$Day[i].balc + test$Day[i-1].balc
}
I identified the line I have written inside the loop is not the correct one,
can someone help me how I can use iteration value(i), for every iteration, as a
basis for changing field names since field consists of 1,2,3... for each
different day( Day1.balc Day2.balc Day3.balc Day4.balc etc.,).
(1) Learn some R (read "An Introduction to R" from the R web page;
manuals). Don't use iteration when you don't need to; i.e. use
vectorised operations whenever possible. (Much faster and clearer.)
(2) Distinguish between data frames and matrices; they are *NOT* the
same thing! What you need here are matrices.
(3) I think this will work for you:
M <- as.matrix(test)
Mnew <- cbind(0,M[,-ncol(M)]) + M
cheers,
Rolf Turner
--
Technical Editor ANZJS
Department of Statistics
University of Auckland
Phone: +64-9-373-7599 ext. 88276
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