[R] Basic vector logic not working

[Daniel Nordlund]

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
> On Behalf Of DimmestLemming
> Sent: Saturday, July 09, 2011 10:31 AM
> To: r-help at r-project.org
> Subject: [R] Basic vector logic not working
> 
> I am interning in a computer science lab and I'm very new to R. The
> language
> basics are clear, but this particular problem isn't:
> 
> I have a very large dataframe called "data" which holds data from Halo
> matches. I'm trying to analyze a certain window such that data$deaths>20
> and
> data$deaths<=27.
> 
> When I enter the line
> 
> kills = data$kills[data$deaths>20]
> 
> or any single condition, it selects the region I want. However, when I
> input
> 
> kills = data$kills[data$deaths>20 && data$deaths<=27]
> 
> "kills" becomes the entire vector data$kills, without selecting any
> specific
> region.
> 
> This is a simple problem, but I can't find anything wrong. How could I fix
> it?
> 

You need to look at the difference between & and &&.  & does position by position comparison, while && only considers the first element of each vector. For your purposes, I believe you should be using a single ampersand,  &.

Hope this is helpful,

Dan

Daniel Nordlund
Bothell, WA USA