[R] Create a new variable

[Erik Iverson]

Hello,

Thomas Jensen wrote:
> Dear R-list,
> 
> Sorry for spamming the list lately, I am just learning the more advanced
> aspects of R! 
> 
> I have some data that looks like this:
> 
> Out Country1 Country 2 Country 3 ... CountryN
> 1	1	1	1		1
> 0	1	1	0		1
> 1	1	0	1		0
> 

Don't paste data like this to the list. Use ?dput to create an easy to 
use data.frame that users of the list can input with one R command.  You 
will most likely get help very quickly at that point since our data will 
match your's exactly.

> I want to create a new variable that counts the number of zeros in every
> row whenever Out is equal to 1, and else it is a zero, so it would look
> like this:
> 
> new_var
> 0 
> 0
> 2
> 
> I have tried the following:
> 
> for (i in length(Out)){
> if (Out == 1) {new_var <- sum(dat[i,] != 1)}
> else {new_var <- 0}
> }
> 
> but this gives me an error message.

I have not tested any of this, but I'm guessing something like the 
following would work.  Assume your data.frame is called df.

#NOT TESTED
tmp <- apply(df, 1, function(x) sum(x == 0))
df$new_var <- ifelse(df$Out == 1, tmp, 0)

See ?apply and ?ifelse .




> 
> Best, Thomas
> 
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