# [R] for loop with multiple conditions in R (e.g. for(i in x & j in y)

arun smartpink111 at yahoo.com
Sat Feb 22 03:05:33 CET 2014

```Hi,
May be this helps:
res.i <- NULL
for(i in seq_along(x)){ res.i <- c(res.i,x[i]-y[i])}

res.ij <- NULL
for(i in seq_along(x)){
for(j in seq_along(y)){
if(i==j){
res.ij <- c(res.ij,x[i]-y[j])
}
}}

identical(x-y,res.i)
#[1] TRUE

identical(res.i,res.ij)
#[1] TRUE
A.K.

I need a for loop that pulls data from two different vectors. For example, suppose that my vectors were
x <- c(1,2,3)
y <- c(4,5,6)
and I wanted a loop that woul take i in x and subtract it from j in y
how would I do it? (i.e. 1-4,2-5,3-6). Note: I realize that for this
silly example there are much better ways to do this than using a for
loop, but the actual script that I am working with is much more
complicated and really does needs to be a for loop, so if you would
humor me and tell me how to write a loop for this example rather than
recommending a better way to solve the example, I would appreciate it.

I've tried the following line of code, but, as expected, it
subtract each value of i from each value of j, which is not what I want,
I want the first value of i subtracted from the first value of j, the
second value of i from the second value of j, etc.
res.i <- c(NULL)
for(i in x){
for(j in y){
sol.i <- i-j
res.i <- c(res.i,sol.i)}
print(res.i)}

thanks!

```