surf plot using meshgrid?

Good day

Pleas advise for code error. First figure is OK. 2nd one is incorrect.

Whei statments z<100 and 100<=z<200 are not taken in to accounte?

x=0:300;
y=x;

[xx,yy]=meshgrid(x,y);

z=(xx+yy)/2;

figure
surf(x,y,z)

if z<100;
    k=z;
elseif z>=100 & z<200;
    k=100;
else
    k=z-100;
end

figure
surf(x,y,k)

Answer 1

[Tommy]

As z is an array, the following two statements

if z<100

and

elseif z>=100 & z<200

will only be true if every element within z satisfies the conditions, so you always end up with the third result (k=z-100).

To apply the if elseif statements to every element within z, try

x=0:300;
y=x;
[xx,yy]=meshgrid(x,y);
z=(xx+yy)/2;
figure
surf(x,y,z,'EdgeColor','none')
k = z;
k(z>=100) = z(z>=100)-100;
k(z>=100&z<200) = 100;
figure
surf(x,y,k,'EdgeColor','none')

[alibaba alibabu]

Thx for prompt help.

Answer 2

[David Hill]

y=x;
[xx,yy]=meshgrid(x,y);
z=(xx+yy)/2;
figure
s=surf(xx,yy,z);
s.EdgeColor = 'none';%turns black if too many points
if z<100
    k=z;
elseif z>=100 & z<200
    k=100;
else
    k=z-100;
end
figure
f=surf(xx,yy,k);
f.EdgeColor = 'none';