R help - Apr 2005 - Display execution in a function

Dear all,

Here is a simplified version of a function I made:

############

plotfunc<-function(x){
#x a vector
cat("please select two points","\n")
plot(x)
points<-locator(2)
return(points)
}

############

Using R version 1.01 for mac os x (aqua GUI)

I would like to know what should I do to make 
sure that my text line will be printed prior to 
the drawing of the plot.
I hope you will agree with me that it is not 
useful to have the plot displayed and R waiting 
for user input while nothing has yet been 
displayed for instructions!

Thanks a lot

PS.:  I have tried this on both a R version 1.01 
and 1.00 and on a G5 dual processor as well as on 
a powerbook G4

Sebastien Durand
--

Dear all I hope you haven't received this message twice,

Here is a simplified version of a function I made:

############

plotfunc<-function(x){
#x a vector
cat("please select two points","\n")
plot(x)
points<-locator(2)
return(points)
}

############

Using the last R version 2.01 for mac os x (v1.01 aqua GUI)

I would like to know what should I do to make 
sure that my text line will be printed prior to 
the drawing of the plot.
I hope you will agree with me that it is not 
useful to have the plot displayed and R waiting 
for user input while nothing has yet been 
displayed for instructions!

Thanks a lot

Sebastien Durand
--

Based on what Jim say yes it works, but if we 
look at the following function, which I beleive 
is properly written.

#############
area.select2<-function(nav,width=6,height=6,...){
	par(ask=TRUE)
	cat("Please select first two opposite 
corner of the working area","\n");
	plot(x=nav[,1],y=nav[,2],"l",col="blue");
	points=locator(2);
	ok<-0;
	while(ok!=1){
		cat("Is your selection correct: YES =1 or NO=0","\n");
		rect(xleft=min(points$x), 
ybottom=min(points$y), xright=max(points$x), 
ytop=max(points$y), density = 0,col = "red", 
border = TRUE);
		ok<-scan("",nlines=1,quiet=TRUE);
		if(ok!=1){
			cat("Please reselect your points","\n");
			points<-locator(2);
		}else{}
	}
	return(points);
}
#############

When run,  using the following call:
#############
area.select(nav=matrix(1:20,10,2))
#############

Even so the text output 'cat("Please reselect 
your points","\n")'  was written previously to 
'points<-locator(2)' , the text does not appears 
at the correct time when I try to select a new 
area.


I really don't understand what is going on there! 
Isn't suppose to be what is written first shall 
happen first!
Could this phenomenon be cause by the locator function...

Cheers!

S?bastien
>Sebastien Durand wrote:
>>Dear all I hope you haven't received this message twice,
>>
>>Here is a simplified version of a function I made:
...snip...
>Setting par(ask=TRUE) before the plot command 
>will require the user to press Enter before the 
>plot is displayed.
>
>Jim

-- 
  S?bastien Durand
Ma?trise en biologie
Universit? de Montr?al
(514) 343-6864
Universit? du Qu?bec ? Montr?al
(514) 987-3000 (1572#)