[R] vector help

[Steve Lianoglou]

Hi Ramya,

On Dec 10, 2009, at 3:29 PM, David Winsemius wrote:

> 
> On Dec 10, 2009, at 2:55 PM, Ramya wrote:
> 
>> 
>> I have tow vectors one is the subset of another
>> 
>> x is a subset of X Both are vectors with n elements
>> 
>> X[X %in% x] would give me x again rite because it is a subset but i want all
>> those are not in x from X.
>> 
>> X[which(X != x)] should this do that

One way to increase your proficiency in R is to break out your statements so that each line does 1 thing.

You should look at the object that `X != x` returns to you. [Shuffle the elements in X and x and then see how that changes for extra credit]

Then look at what `which(X != x)` gives you.

Doing that, you'd see why what you tried originally didn't work.

> 
> Perhaps you think R _should_ read your mind, but we are not there yet. Try instead:
> 
> X[!(X %in% x)]

There are also set-like functions in R, which might fit your brain-way of thinking:

Get elements that are in both x and X:
intersect(X,x)

Get elements in X that are not in x
setdiff(X,x)


--
Steve Lianoglou
Graduate Student: Computational Systems Biology
  |  Memorial Sloan-Kettering Cancer Center
  |  Weill Medical College of Cornell University
Contact Info: http://cbio.mskcc.org/~lianos/contact