---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- # P() lets you click a point and read its coordinates. This is useful in all cases # where you have to deal with graphics and images. It can also be useful for drawing # figures; for example: HF=3; BF=3; PLANE(0,10, 0,10) P() # I click more or less at point 5,9 and get: # xP <- ... ; yP <- ... # Then I reproduce each of the following lines and click more or less in 2,2 8,2 5,9 x <- xP; y <- yP; P(); segm(xP,yP, x,y, "red") # xP <- ... ; yP <- ... I do things like this after the next two lines x <- xP; y <- yP; P(); segm((xP,yP, x,y, "red") x <- xP; y <- yP; P(); segm((xP,yP, x,y, "red") # I get the red triangle on the left: # Similarly, sketch the blue figure: P() x <- xP; y <- yP; P(); segm(xP,yP, x,y, "blue") x <- xP; y <- yP; P(); segm(xP,yP, x,y, "blue") # Then if I want to reproduce the figure without scale, I can use the x,y values printed # out, getting the figure to the right (if I use "broken" I would have thicker lines) PLANEww(0,10, 0,10) x <- c(2,8,5,2); y <- c(2,2,9,2); polyl(x,y, "red") x <- c(6,5,4); y <- c(2,5,2); polyl(x,y, "blue")