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[S] Straight lines appear wavy with "perspp"

To: s-news@wubios.wustl.edu
Subject: [S] Straight lines appear wavy with "perspp"
From: "Spencer B. Graves" <sgraves@prodsyse.com>
Date: Thu, 21 May 1998 11:02:48 -0500
Sender: owner-s-news@wubios.wustl.edu
Straight lines and gentle curves appear unacceptably wavy 
in an S-PLUS perspective plot (S-PLUS 3.3 or 4.0 under 
Windows 95).  This is illustrated by the following function 
"plot.persp.test". 

Thanks, 
Spencer Graves

Any suggestions on how to get around this?  
******************
plot.persp.test <- function(){
#       A straight line appears unacceptably wavy in an S-PLUS 
#       perspective plot.  I've traced the problem to excessive 
#       round off in a single precision Fortran function, but I 
#       don't know enough about the algorithm to correct it.  
#
#       How can I get around this problem?  
#
        z0 <- array(c(0, 0, 1, 1), dim = c(2, 2))
        persp0 <- persp(x = c(0, 1), y = c(0, 1), z = z0)
        x1 <- seq(0, 1, length = 99)
        persp1 <- perspp(x = x1, y = x1, z = x1, from.persp = persp0)
        lines(persp1)
        persp1 <- perspp(x = x1, y = x1^2, z = x1, from.persp = persp0)
        lines(persp1)
}

****************************************
Spencer Graves, PhD, statistician and engineer improving productivity.  
Productive Systems Engineering,  751 Emerson Ct., San Jose, CA 95126, 
http://www.prodsyse.com, tel: (408)294-5779 / fax: (408)294-2343, and 
Univ. of Wisconsin Center for Quality and Productivity Improvement,  
610 Walnut St., Madison, WI 52705, tel:(608)263-2652, fax:(608)263-1425
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