Sia F(x,y) =(x^2+x*y+5*y^2+x-y)*exp(-(x^2+y^2)). Studia la funzione utilizzando R per tracciarne il grafico e le curve di livello e operando opportuni zoom. Individuane, arrotondandone le coordinate a 2 cifre, i punti di estremo relativo e i punti di sella. Suggerimento: parti studiando la funzione per x in [−4,4] e y in [−4,4].
F <- function(x,y) (x^2+x*y+5*y^2+x-y)*exp(-(x^2+y^2)) x1 <- -4; x2 <- 4; y1 <- -4; y2 <- 4 x <- seq(x1,x2,len=31); y <- seq(y1,y2,len=31); z <- outer(x,y,F) persp(x,y,z,theta=40,phi=5, col="yellow", shade=0.3,ticktype="detailed",cex.axis=0.7,cex.lab=0.7) ## x1 <- -3; x2 <- 3; y1 <- -3; y2 <- 3 x <- seq(x1,x2,len=31); y <- seq(y1,y2,len=31); z <- outer(x,y,F) persp(x,y,z,theta=40,phi=5, col="yellow", shade=0.3,ticktype="detailed",cex.axis=0.7,cex.lab=0.7) ## x1 <- -2.5; x2 <- 2.5; y1 <- -2.5; y2 <- 2.5 x <- seq(x1,x2,len=31); y <- seq(y1,y2,len=31); z <- outer(x,y,F) persp(x,y,z,theta=220,phi=75, col="yellow", shade=0.3,ticktype="detailed",cex.axis=0.7,cex.lab=0.7) # dev.new() contour(x,y,z); abline(v=axTicks(1),h=axTicks(2),lty=3,col="grey70") # x1 <- -1.8; x2 <- 1; y1 <- -1.5; y2 <- 1.5 x <- seq(x1,x2,len=31); y <- seq(y1,y2,len=31); z <- outer(x,y,F) contour(x,y,z); abline(v=axTicks(1),h=axTicks(2),lty=3,col="grey70") # dev.new() x1 <- 0.1; x2 <- 0.4; y1 <- 0.8; y2 <- 1.2 x <- seq(x1,x2,len=31); y <- seq(y1,y2,len=31); z <- outer(x,y,F) contour(x,y,z); abline(v=axTicks(1),h=axTicks(2),lty=3,col="grey70") # x1 <- 0.26; x2 <- 0.29; y1 <- 0.96; y2 <- 1.04 x <- seq(x1,x2,len=31); y <- seq(y1,y2,len=31); z <- outer(x,y,F) contour(x,y,z); abline(v=axTicks(1),h=axTicks(2),lty=3,col="grey70") # dev.new() x1 <- -0.6; x2 <- 0; y1 <- 0; y2 <- 0.3 x <- seq(x1,x2,len=31); y <- seq(y1,y2,len=31); z <- outer(x,y,F) contour(x,y,z); abline(v=axTicks(1),h=axTicks(2),lty=3,col="grey70") # x1 <- -0.45; x2 <- -0.4; y1 <- 0.12; y2 <- 0.15 x <- seq(x1,x2,len=31); y <- seq(y1,y2,len=31); z <- outer(x,y,F) contour(x,y,z); abline(v=axTicks(1),h=axTicks(2),lty=3,col="grey70") # dev.new() x1 <- -0.1; x2 <- 0.1; y1 <- -1; y2 <- -0.9 x <- seq(x1,x2,len=31); y <- seq(y1,y2,len=31); z <- outer(x,y,F) contour(x,y,z); abline(v=axTicks(1),h=axTicks(2),lty=3,col="grey70") # x1 <- -0.04; x2 <- 0.04; y1 <- -0.98; y2 <- -0.94 x <- seq(x1,x2,len=31); y <- seq(y1,y2,len=31); z <- outer(x,y,F) contour(x,y,z); abline(v=axTicks(1),h=axTicks(2),lty=3,col="grey70") # x1 <- -0.005; x2 <- 0.01; y1 <- -0.96; y2 <- -0.95 x <- seq(x1,x2,len=31); y <- seq(y1,y2,len=31); z <- outer(x,y,F) contour(x,y,z); abline(v=axTicks(1),h=axTicks(2),lty=3,col="grey70") # x1 <- 0.004; x2 <- 0.0056; y1 <- -0.957; y2 <- -0.954 x <- seq(x1,x2,len=31); y <- seq(y1,y2,len=31); z <- outer(x,y,F) contour(x,y,z); abline(v=axTicks(1),h=axTicks(2),lty=3,col="grey70") # dev.new() x1 <- 0.6; x2 <- 1; y1 <- -0.2; y2 <- 0.2 x <- seq(x1,x2,len=31); y <- seq(y1,y2,len=31); z <- outer(x,y,F) contour(x,y,z); abline(v=axTicks(1),h=axTicks(2),lty=3,col="grey70") # x1 <- 0.84; x2 <- 0.88; y1 <- -0.04; y2 <- 0.08 x <- seq(x1,x2,len=31); y <- seq(y1,y2,len=31); z <- outer(x,y,F) contour(x,y,z); abline(v=axTicks(1),h=axTicks(2),lty=3,col="grey70") # x1 <- 0.85; x2 <- 0.87; y1 <- 0.01; y2 <- 0.03 x <- seq(x1,x2,len=31); y <- seq(y1,y2,len=31); z <- outer(x,y,F) contour(x,y,z); abline(v=axTicks(1),h=axTicks(2),lty=3,col="grey70") # dev.new() x1 <- -2; x2 <- -1; y1 <- -1; y2 <- 1 x <- seq(x1,x2,len=31); y <- seq(y1,y2,len=31); z <- outer(x,y,F) contour(x,y,z); abline(v=axTicks(1),h=axTicks(2),lty=3,col="grey70") # x1 <- -2; x2 <- -1.2; y1 <- 0; y2 <- 0.5 x <- seq(x1,x2,len=31); y <- seq(y1,y2,len=31); z <- outer(x,y,F) contour(x,y,z); abline(v=axTicks(1),h=axTicks(2),lty=3,col="grey70") # x1 <- -1.7; x2 <- -1.5; y1 <- 0.25; y2 <- 0.35 x <- seq(x1,x2,len=31); y <- seq(y1,y2,len=31); z <- outer(x,y,F) contour(x,y,z); abline(v=axTicks(1),h=axTicks(2),lty=3,col="grey70")