R help - Mar 2009 - plotting two variables with a third used for color

I have a problem where I have two columns of data that I can simply plot using:

plot(wV[0:15,3],wY[0:15,3]).  

This produces my desired plot.

Now, say I have a third variable that I would like to introduce and use that
variable to set different colors in the plot

In this case, say I wanted values greater than 0 to be "blue" and
values less than 0 to be "red"

Basically, my question is how can one plot something like the function shown
above, but with the added functionality of indicating color for a third variable

Something to the effect:

if(weightComply[0:15,3]>0)  //if the values from 0 to 15 in column 3 are
greater than 0
plot(wV[0:15,3],wY[0:15,3],col="blue")   //then plot the dots as blue 

else
plot(wV[0:15,3],wY[0:15,3],col="red")  //otherwise plot the dots red

 I know this syntax is wrong, but I think it shows what I generally want to do.

Mark

On Mar 20, 2009, at 3:55 PM, Altaweel, Mark R. wrote:
> I have a problem where I have two columns of data that I can simply  
> plot using:
>
> plot(wV[0:15,3],wY[0:15,3]).
>
Perhaps:
plot(wV[0:15,3],wY[0:15,3], col = ifelse(wY[0:15,3]>0,
"blue","red") )
> This produces my desired plot.
>
> Now, say I have a third variable that I would like to introduce and  
> use that variable to set different colors in the plot
>
> In this case, say I wanted values greater than 0 to be "blue" and
> values less than 0 to be "red"
And if they are zero? In my example those become red. Basically you  
create a vector that is as long as the y-values with values of "red"  
or "blue" that depend on your criterion.
>
>
> Basically, my question is how can one plot something like the  
> function shown above, but with the added functionality of indicating  
> color for a third variable
>
> Something to the effect:
>
> if(weightComply[0:15,3]>0)  //if the values from 0 to 15 in column 3  
> are greater than 0
> plot(wV[0:15,3],wY[0:15,3],col="blue")   //then plot the dots as
blue
>
> else
> plot(wV[0:15,3],wY[0:15,3],col="red")  //otherwise plot the dots
red
>
> I know this syntax is wrong, but I think it shows what I generally  
> want to do.
>
> Mark
David Winsemius, MD
Heritage Laboratories
West Hartford, CT

On 2009-March-20  , at 16:23 , David Winsemius wrote:
> On Mar 20, 2009, at 3:55 PM, Altaweel, Mark R. wrote:
>
>> I have a problem where I have two columns of data that I can simply  
>> plot using:
>>
>> plot(wV[0:15,3],wY[0:15,3]).
>>
> Perhaps:
> plot(wV[0:15,3],wY[0:15,3], col = ifelse(wY[0:15,3]>0,
"blue","red") )
And you could look into the package ggplot2 which gives you a legend  
and is well suited for these things.

# quick version:
qplot(wV[0:15,3], wY[0:15,3],
colour=ifelse(wY[0:15,3]>0,">0","<0"))

# more explicit version, using a data.frame
dat = data.frame(v=wV[0:15,3], y=wY[0:15,3],  
sign=ifelse(wY[0:15,3]>0,">0","<0"))
ggplot(data=dat) + geom_point(aes(x=v,y=y,colour=sign))

JiHO
---
http://jo.irisson.free.fr/