On 16/06/11 11:07, Aimee Jones wrote:
Hi all,
My apologies if this message is incredibly inept but I am very new to both
computer programming and to R.
I am working with the odesolve add-on and have the following function
defined
RVF_Single<- function(t, x, p)
within the script I also have the following functions defined:
T1<-function(t) {T1<-27.5-12.5*cos(2*pi*t/365)}
and
B1<-function(T1,t) {B1<-dnorm(T1(t),mean=22.5,sd=3.3)}
Actually your code should read:
T1<-function(t) {27.5-12.5*cos(2*pi*t/365)}
and
B1<-function(T1,t) {dnorm(T1(t),mean=22.5,sd=3.3)}
i.e. don't assign the value that you calculate in the code; this
is the value ***returned*** by the function. What you is in effect
harmless here, but it is confusing and could cause problems in
other contexts.
When the script is run it doesn't return an error message but the graphs
returned are "wrong". When I input "plot(T1,0,3650)" it returns the plot of
T1 as expected---a series of waves between 15 and 40, BUT when I input
"plot(B1,0,3650)" I get an error message of "Error in 2 * pi * t : 't' is
missing".
Can anyone advise as to why t registers for function T1 but disappears for
function B1?
Well, T1() a function of ***t*** only (where t is the variable against which
you expect the values of T1() to be plotted. Whereas, B1 is a function of
two variables T1 and t, which confuses things.
Note that by calling plot() in this way you are in fact calling
plot.function()
which is in fact a wrapper for curve(). As has been discussed recently on
this list, the syntax for curve() is a bit delicate.
A workaround for your problem is:
plot(function(t){B1(T1,t)},0,3650)
HTH
cheers,
Rolf Turner
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