R help - Aug 2009 - help with recalling data points in a specific region of the plot

Hi all,

Is there a quick way to display or recall data points from a specific region
on the plot? For example I want the points from x>5 and y>5?
Thank you very much!

-- 
Edward Chen

	[[alternative HTML version deleted]]

I am assuming that you want to desplay all the data and highlight the subset.
Set up a vector to indicate the breakdown of the data and you can do it fairly
easily in ggplot2 if you treat the vector as a factor.

library(ggplot)
mydata <- data.frame(x=1:21, y= -10:10)
z <- ifelse(mydata[,1]>5 & mydata[,2] >5, 1, 0) # identify points
>5
mydata <- data.frame(mydata, z)
ggplot(mydata, aes(x=x, y=y, colour= factor(z))) + geom_point() 

--- On Mon, 8/24/09, Edward Chen <edchen51 at gmail.com> wrote:
> From: Edward Chen <edchen51 at gmail.com>
> Subject: [R] help with recalling data points in a specific region of the
plot
> To: r-help at r-project.org
> Received: Monday, August 24, 2009, 12:55 PM
> Hi all,
> 
> Is there a quick way to display or recall data points from
> a specific region
> on the plot? For example I want the points from x>5 and
> y>5?
> Thank you very much!
> 
> -- 
> Edward Chen
> 
> ??? [[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help at r-project.org
> mailing list
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> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained,
> reproducible code.
> 

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On Aug 24, 2009, at 12:55 PM, Edward Chen wrote:
> Hi all,
>
> Is there a quick way to display or recall data points from a  
> specific region
> on the plot? For example I want the points from x>5 and y>5?
> Thank you very much!
>
Your question is pretty light on specifics but assuming that you have  
columns  x and y  in a dataframe, df1, then in ordinary graphics you  
could just execute this after another plotting function has been  
performed:

with(subset(df1, x>5 & y>5), points(x,y, col="red") )

# I generally make my points smaller with cex=0.2 or cex=0.1

subset(f1, x>5 & y>5)[ , c("x","y")]
# should "recall" the values, if my wetware R interpreter is working  
properly.

David Winsemius, MD
Heritage Laboratories
West Hartford, CT

On Aug 24, 2009, at 6:50 PM, Edward Chen wrote:
> Thank you so much for your reply. I apologize for not making my  
> question clearer.
> The problem I have right now is not just a matrix. I have a plot in  
> which the X and Y are both calculated by other functions before the  
> plot. After reviewing the plot, there are some areas of the plot  
> that do not look correct. I just want to know if there's a way to  
> know what the x and y coordinate of those points are and display  
> them on the graph if possible. the specific region that I am looking  
> for is 0<x<1 and y<0.5. Hope this would clarify some confusions.
> Thank you again!
Two thoughts
a)  which would seem that the blindingly obvious strategy ... no  
dataframe? Then make one:

df1 <- data.frame(X =X, Y=Y)

    .... and proceed as suggested.

... or try .... still using your original limits:

with(df1[df1$X>5&df1$Y>5, ], text(X, Y,
          paste( sprintf(fmt="%0.2f", X), 
sprintf(fmt="%0.2f", Y) ) ) )

... or print their row numbers ....

df1$Rw <- 1:nrow(df1)

with(df1[df1$X>5&df1$Y>5, ], text( X, Y, paste("row=", Rw) )
)

b) the dataframeless approach:  create an index for the joint  
conditions on X and Y and then use that index to reference their  
values. To use you new conditions, that would be;

idx <- X > 0 & X < 1 & Y < 0.5
plot(X[idx], Y[idx], col="red"")

... or print the (X,Y) values with sprintf as illustrated above.


>
> On Mon, Aug 24, 2009 at 10:52 AM, David Winsemius <dwinsemius at
comcast.net
> > wrote:
>
> On Aug 24, 2009, at 12:55 PM, Edward Chen wrote:
>
> Hi all,
>
> Is there a quick way to display or recall data points from a  
> specific region
> on the plot? For example I want the points from x>5 and y>5?
> Thank you very much!
>
> Your question is pretty light on specifics but assuming that you  
> have columns  x and y  in a dataframe, df1, then in ordinary  
> graphics you could just execute this after another plotting function  
> has been performed:
>
> with(subset(df1, x>5 & y>5), points(x,y, col="red") )
>
> # I generally make my points smaller with cex=0.2 or cex=0.1
>
> subset(f1, x>5 & y>5)[ , c("x","y")]
> # should "recall" the values, if my wetware R interpreter is
working
> properly.
>
>
> -- 
> Edward Chen
David Winsemius, MD
Heritage Laboratories
West Hartford, CT