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Plotting multiple ablines

5 messages · Rolf Turner, Uwe Ligges, r at quantide.com +1 more

Thomas Levine
# 
I really want to do this:

abline(
a=tan(-kT*pi/180),
b=kY-tan(-kT*pi/180)*kX
)

where kX,kY and kT are vectors of equal length. But I can't do that
with abline unless I use a loop, and I haven't figured out the least
unelegant way of writing the loop yet. So is there a way to do this
without a loop?

Or if I am to resort to the loop, what's the best way of doing it
considering that I have some missing data? Here's the mess that I
wrote.

converge <- na.omit(data.frame(kX,kY,kT))
for (z in (length(converge$kT)))
{abline(
a=tan(converge$kT[z]*pi/180),
b=converge$kY[z]-tan(-converge$kT[z]*converge$kX[z]*pi/180)
)}

I think the missing data are causing the problem; this happens when I run:

Error in int_abline(a = a, b = b, h = h, v = v, untf = untf, ...) :
  'a' and 'b' must be finite
Rolf Turner
#
On 2/04/2009, at 7:04 AM, Thomas Levine wrote:

            

      
      
      
    

        
The help for abline explicitly states that a and b must be ``single  
values'';
so no vectorization appears to be possible, as abline is currently  
written.
Hence you are stuck with a for-loop.

There appears to be nothing wrong with the for-loop that you've written,
at first blush at least.

There won't be NAs in ``converge'' since you've very cleverly used  
na.omit.
So ``missing data'' are NOT the problem.

The problem is then (probably) that some of your data are yielding  
infinite
values of tan().

***Look*** at the values in converge.  ***Look*** at the values of a  
and b
produced in your loop and see where you're getting infinite values.

	cheers,

		Rolf Turner

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      Uwe Ligges
    

    

      
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Rolf Turner wrote:

            

      
      
      
    

        
Or use mapply(). Untested:

mapply(abline, tan(converge$kT * pi / 180),
        converge$kY - tan(-converge$kT * converge$kX * pi / 180))

Uwe Ligges

            

      
      
      
    

        

      
      
    

  
  


  


      

    

    

      
      

        


  

        

      r at quantide.com
    

    

      
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May be:

plot(c(-1, 1) , c(-1, 1), type = "n")
n = 4
a = rep(0, n)
b = 1:n/n


fun = function(i, a, b, col = 1 , ...) {
    abline(a[i], b[i], col = col[i], ...)
}

lapply(1:n, fun, a=a, b=b, col = 1:n)

Andrea

        
Thomas Levine wrote:

            

      
      
      
    

        

      
      
    

  
  


  


      

    

    
1 day later