library(tcltk)
n<-50
set.seed(101)
x<-rnorm(n)
x[15]<- -x[14]
y<-0.4*x + 0.1*rnorm(n,0,2)
y[14]<-0.4*x[14]
y[15]<--y[14]
x[1]<-max(x)

grafica<-function(...){theta=as.numeric(tclvalue(SliderValue));
                       plot(x,y,ylim=c(-3,3),xlim=c(-3,3),pch=19);
                       #points(cos(theta)*x +sin(theta)*y,rep(-1,n),pch=19,col="red");
                       points(0,0,pch=19)
                       abline(a=0,b=tan(theta),col="red",lwd=2)
                       points(cos(theta)*x +sin(theta)*y,rep(-3,n),pch=19,col="red",) 
                       points(x[1],y[1],col="blue",pch=19,cex=1.5)
                       points(x[15],y[15],col="green",pch=19)
                       points(x[14],y[14],col="green",pch=19)
                       xp1<-cos(theta)*(cos(theta)*x[1] +sin(theta)*y[1]);
                       yp1<-sin(theta)*(cos(theta)*x[1] +sin(theta)*y[1])
                       lines(c(x[1],xp1),c(y[1],yp1),col="green")
                       points(xp1,yp1,pch=19,col="red",cex=1.5);
                       points(cos(theta)*x[1] +sin(theta)*y[1],-3,pch=19,col="blue",cex=1.5)
                       points(cos(theta)*x[15] +sin(theta)*y[15],-3,pch=19,col="green")
                       points(cos(theta)*x[14] +sin(theta)*y[14],-3,pch=19,col="green")
                       }



sliderinicio=-0.999;
slidermin=-1;
slidermax=1.95;
sliderstep=0.01


tt <- tktoplevel()
SliderValue <- tclVar(sliderinicio)
SliderValueLabel <- tklabel(tt,text=as.character(tclvalue(SliderValue)))
tkgrid(tklabel(tt,text="Slider Value : "),SliderValueLabel,tklabel(tt,text="angulo"))
tkconfigure(SliderValueLabel,textvariable=SliderValue)
slider <- tkscale(tt, from=slidermin, to=slidermax,
                   showvalue=F, variable=SliderValue, resolution=sliderstep, 
                   command=grafica)

tkgrid(slider)
tkfocus(tt)