Erasing part of contourf diagram (L-shaped diagram using contourf)

I have three matrices. First one is values of temperatures in (x,y) points, and second and third matrix is x and y coordinates, respectively. Rectangular block with temperatures is on figure(1) and it looks appropriately, but when I tried to neglect the values x>2 and y<2, to get L-shaped diagram, it doesn't look fine. Is there any solution to this problem? I submit the picture how the figure(2) should look.

Temp=[20 20 20 20 20;   % y=0
      18 18 18 18 18;   % y=1
      16 16 16 16 16;   % y=2
      14 14 14 14 14;   % y=3
      12 12 12 12 12];  % y=4
x_points=[0 1 2 3 4;   
          0 1 2 3 4;
          0 1 2 3 4;
          0 1 2 3 4;
          0 1 2 3 4];
y_points=[0 0 0 0 0;   
          1 1 1 1 1;
          2 2 2 2 2;
          3 3 3 3 3;
          4 4 4 4 4];
figure(1) % Rectangular block with temperatures
contourf(x_points,y_points,Temp)
figure(2) % L-shaped block with temperatures
Temp1=Temp
Temp1(1:2,4:5)=NaN
contourf(x_points,y_points,Temp1)

Answer 1

[darova]

try

ind = x_points > 2 & y_points < 2;
temp(ind) = nan;

[FEM_Analysis_1000]

Again, the same diagram like in my case. This part of the code is attached below. Probably, since we have temperature values in discrete points (integer numbers between 0 and 4), there is no way get the diagram I want. We will always have a "jump" in region (2<x<3 & 1<y<2) for this choice of NaN points.

figure(2) % L-shaped block with temperatures
Temp1=Temp
Temp1(1:2,4:5)=NaN
contourf(x_points,y_points,Temp1)