Refer to columns by position rather than name and everything is simpler:
for (i in 2:4 ) {
test[, i] <- test[, i] + test[, i-1]
}
Note your approach fails on the first line since you start with i=1 and there
is no Day0. Another approach that is simpler:
t(apply(test, 1, cumsum))
David L. Carlson
Department of Anthropology
Texas A&M University
-----Original Message-----
From: R-help [mailto:r-help-boun...@r-project.org] On Behalf Of Vijaya Kumar
Regati
Sent: Tuesday, May 30, 2017 3:44 AM
To: Manjusha Joshi <manjusha.jo...@gmail.com>
Cc: r-help@R-project.org; vijaykr....@gmail.com
Subject: Re: [R] Need Help - R Programming - Using iteration value to change
field names for processing for every iteraion
Hi Manjusha,
Thank you for the response. That surely helps.
But the major issue in my case is not how we can apply sum fn, but how we can
change field names based on iteration number.
I cant skip loop in my case, because in real situation I have to deal with say
around 100 fields, the only thing that changes is Day number in field name and
the iteration number should be able to handle that.
With Regards,
Vijaya Kumar Regati
Technical Lead, M3bi India Private Ltd
Work: 040-67064732
________________________________
From: Manjusha Joshi <manjusha.jo...@gmail.com>
Sent: Tuesday, May 30, 2017 1:42:10 PM
To: Vijaya Kumar Regati
Cc: r-help@R-project.org; vijaykr....@gmail.com
Subject: Re: [R] Need Help - R Programming - Using iteration value to change
field names for processing for every iteraion
Hello Vijaya,
On Tue, May 30, 2017 at 12:32 PM, Vijaya Kumar Regati
<vijayakumar.reg...@m3bi.com<mailto:vijayakumar.reg...@m3bi.com>> 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.,).
There are many built in functions in R which will help to avoid loops.
Try 'cumsum' to add entries in a row to get cumulative sum. Use 'apply' to
avoid loops.
df is the dataframe in which your data has been stored.
t(apply,df,1,cumsum)
will give you the required results.
Please check help of 'apply' for more details.
Best wishes,
______________________________________________
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--
Manjusha S. Joshi
Mobile: 09822 319328
Pune, India
blog:http://manjushajoshi.wordpress.com/
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______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
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