[R] Add sums across chosen columns. ... was (No Subject)

[David Winsemius]

On Aug 23, 2013, at 9:41 AM, Anindya Sankar Dey wrote:

> You can easily subset the data then use rowSum.
> 
> say your dataset name is data1.
> 
> then write data2<-data[,c(7,12,45,57)]
> 
> then write result<-rowsum(data2)

In R there are two different functions `rowsum` and `rowSums`. The use you are describing sounds like a case rowSums, rather than `rowsum`. For reasons that are unclear to me `rowsum` seems to be more like `grouped.colSums` than anything I would have imagined it to be just looking at its name and then looking at its help page.

I think you wanted:

dfrm$m <- rowSums( dfrm[, c(7,12,57,45) ] ) # assuming dfrm is a dataframe.

-- 
David.

> 
> 
> On Fri, Aug 23, 2013 at 3:47 PM, rajib prasad <rwho2007 at gmail.com> wrote:
> 
>> I am new to R. I have a data like:
>> 
>>                              x      y       z      w       p  ..........
>>     m
>>                       1     10    15     20     25     30
>>                       2     11     16    21     26     31
>>                       3      12     17    18    19     20
>>                       4      51     52    53    55    67
>>                 .......
>> 
>> thus I have 145 rows and 160 column in my data which is named as
>> data.csv.  Now i want to create a new column 'm' and for every row m
>> will take value =column 7+ column 12+ column 57+ column 45 i.e. for
>> every row it will take value of sum of corresponding row's 7 & 12 & 57
>> & 45 column's value .
>> So, how to write the code for this operation?
>> 


David Winsemius
Alameda, CA, USA