[R] How to sum values across multiple variables using a wildcard?

[Simon Blomberg]

data <- data.frame(var1=c(1,2,3), var2=c(3,4,5), var3=c(4,5,6), foo = 
c(100,200,300))
# sum rows with "var" in their name
rowSums(data[, grep("var", names(data))])

 1  2  3
 8 11 14



mtb954 at gmail.com wrote:
> I have a dataframe called "data" with 5 records (in rows) each of
> which has been scored on each of many variables (in columns).
>
> Five of the variables are named var1, var2, var3, var4, var5 using
> headers. The other variables are named using other conventions.
>
> I can create a new variable called var6 with the value 15 for each
> record with this code:
>
>   
>> var6=var1+var2+var3+var4+var5
>>     
>
> but this is tedious for my real dataset with dozens of variables. I
> would rather use a wildcard to add up all the variables that begin
> with "Var" like this pseudocode:
>
>   
>> Var6=sum(var*)
>>     
>
> Any suggestions for implementing this in R? Thanks! Mark
>
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-- 
Simon Blomberg, B.Sc.(Hons.), Ph.D, M.App.Stat.
Centre for Resource and Environmental Studies
The Australian National University
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