How to color a small squared or half squared zone of the plot?

Hi, everyone, here it is graph between P vs t, as shown below and the data is also attached here. I want shade a say light blue color in the squre zone having Y axis limit 1865 - 1890. The shade should be in transparent color and plot have to be in stairs and visible within shade zone. How I acn do it, if not complete squared zone, then left half part with same y axis limits should be in colored patch.

Answer 1

[KSSV]

B = [23 1865; 36 1865; 36 1890 ; 23 1890] ;
patch(B(:,1),B(:,2),'b') ;
hold on
plot(p,t) ; 

[Nisar Ahmed]

@KSSV I am trying this way and it is not working, can you please see whrere is error.

subplot(1,5,2); B = [23 1865; 36 1865; 36 1890 ; 23 1890]; patch(B(:,1),B(:,2),'b');

stairs(P,T,'k'); set(gca, 'ydir', 'reverse');

[KSSV]

You need to use hold on.

subplot(1,5,2); 
B = [20 1865; 40 1865; 40 1890 ; 20 1890]; 
patch(B(:,1),B(:,2),'b');  
hold on
stairs(p,t,'k'); 
set(gca, 'ydir', 'reverse'); 
box on

[Nisar Ahmed]

@KSSV Thank you very much, it is working now