[R] Vector Assignments

[Gabor Grothendieck]

If you were using the colours in a model matrix
using a factor would be best but since your case
is plotting using characters is best.


 
Date: 03 Dec 2003 08:26:05 -0500 
From: Arend P. van der Veen <apv at capital.net>
To: R HELP <r-help at stat.math.ethz.ch> 
Subject: Re: [R] Vector Assignments 

 
 
Your recommendations have worked great. I have found both cut and
ifelse to be useful.

I have one more question. When should I use factors over a character
vector. I know that they have different uses. However, I am still
trying to figure out how I can best take advantage of factors. 

The following is what I am really trying to do:

colors <- c("red","blue","green","black")
y.col <- colors[cut(y,c(-Inf,250,500,700,Inf),right=F,lab=F)]
plot(x,y,col=y.col)

Would using factors make this any cleaner? I think a character vector
is all I need but I thought I would ask.

Thanks for your help,
Arend van der Veen



On Tue, 2003-12-02 at 00:32, Gabor Grothendieck wrote:
> And one other thing. Are you sure you want character variables
> as the result of all this? A column whose entries are each one
> of four colors seems like a good job for a factor:
> 
> colours <- c("red", "blue", "green","black")
> cut(x, c(-Inf,250,500,700,Inf),right=F,lab=colours)
> 
> 
> 
> ---
> Date: Mon, 1 Dec 2003 23:47:39 -0500 (EST) 
> From: Gabor Grothendieck <ggrothendieck at myway.com>
> To: <h.wickham at auckland.ac.nz>, <apv at capital.net> 
> Cc: <r-help at stat.math.ethz.ch> 
> Subject: Re: [R] Vector Assignments 
> 
> 
> 
> 
> 
> Just some small refinements/corrections:
> 
> colours <- c("red", "blue", "green","back")
> colours[cut(x, c(-Inf,250,500,700,Inf),right=F,lab=F)]
> 
> ---
> Date: Tue, 02 Dec 2003 14:38:55 +1300 
> From: Hadley Wickham <h.wickham at auckland.ac.nz>
> To: Arend P. van der Veen <apv at capital.net> 
> Cc: R HELP <r-help at stat.math.ethz.ch> 
> Subject: Re: [R] Vector Assignments 
> 
> 
> 
> One way would be to create a vector of colours and then cut() to index 
> the vector:
> 
> colours <- c("red", "blue", "green","back")
> colours[cut(x, c(min(x),250,500,700,max(x)),lab=F)]
> 
> Hadley
> 
> 
> Arend P. van der Veen wrote:
> 
> >Hi,
> >
> >I have simple R question. 
> >
> >I have a vector x that contains real numbers. I would like to create
> >another vector col that is the same length of x such that:
> >
> >if x[i] < 250 then col[i] = "red"
> >else if x[i] < 500 then col[i] = "blue"
> >else if x[i] < 750 then col[i] = "green"
> >else col[i] = "black" for all i
> >
> >I am convinced that there is probably a very efficient way to do this in
> >R but I am not able to figure it out. Any help would be greatly
> >appreciated.
> >
> >Thanks in advance,
> >Arend van der Veen
> >
> 
> 
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