例の密度関数

#pdf
x=seq(-0.5,2.5,length=50)
y=seq(-0.5,1.5,length=50)
pdf=function(x,y){
	if(((0<=x)&&(x<=2))&&((0<=y)&&(y<=1))){
		(3/7)*(2-x)*(x+y)
	}else{
		return(0)
	}
}

z=matrix(0,50,50)
z
for(i in 1:50){
	for(j in 1:50){
		z[i,j]=pdf(x[i],y[j])
	}
}
persp(x,y,z,theta = 150, phi = 30, expand = 0.5, col = "lightblue",zlim=c(0,1))


#df
x=seq(-1,3,length=50)
y<-x
df1=function(x,y){
	if((x<=0)||(y<=0)){
		return(0)
	}else if(((0<x)&&(x<=2))&&((0<y)&&(y<=1))){
		(3/7)*x*y*(x+y-(1/3)*x^2-(1/4)*x*y)
	}else if(((0<x)&&(x<=2))&&(y>1)){
		(3/7)*x*(1+(3/4)*x-(1/3)*x^2)
	}else if((x>2)&&((0<y)&&(y<=1))){
		(6/7)*y*((2/3)+(1/2)*y)
	}else{
		return(1)
	}
}

for(i in 1:50){
	for(j in 1:50){
		z[i,j]=df1(x[i],y[j])
	}
}
persp(x,y,z,theta = 0, phi = 30, expand = 0.5, col = "lightblue",zlim=c(0,1))