MATLAB: How to plot a region in a Matlab plot

fill region in a 2d plotMATLAB

Hi All,
I want to shade(filled) several regions in a 2D plot by different colors. The attachment contains the plot I am expecting to plot. I could not find a better tutorial to plot this figure yet. Could you please give some help on this. Thank you in advance.
The boundaries of the given region is given by following functions. 
P1 =   range from 0 to 5
temp = range from 600 to 1600
Tttg1 = 760.-60.*(P1-1.)**2.           
Tttg2 = 1000.-150.*((P1-1.2)/1.2)**2.    
Pttg1 = -0.5*((temp-870.)/220.)     
Pttg2  = 1.5+0.7*((temp-700.)/200.) 
Pttg3 = 1.     
Tttg3 = 1000.                        #    pr3
Tttg4 = 1100.+50.*((P1-3.5)/3.5)**2.  #     pr4
Pttg4 = 2.35 +0.15*((temp-1000.)/100.)  #    Tr4/1000
Pttg5  =5.
%3 regions
lpttg_con = (temp>Tttg1) & (temp<Tttg2) & (P1>Pttg1) & (P1<Pttg2) & (P1<Pttg3)# & matcon_WB
mpttg_con = (temp>Tttg1) & (temp<Tttg2) & (P1>Pttg1) & (P1<Pttg2) & (P1>=Pttg3)# & matcon_WB
hpttg_con = (temp>Tttg3) & (temp<Tttg4) & (P1>Pttg4) & (P1<Pttg5)
Thanks
Prasanna

Best Answer

here is quick example of what you can do by putting the regions as an image under the plots:
%gen xy spans
temps=0:.1:100;
press = 0:.1:100;
[x y] = meshgrid(temps,press);
%generate the binary mask regions
r1 = x.^2+y.^2<50;
r2 = (x-50).^2+(y-75).^2<50^2;
figure(1),imagesc(r1,'XData',temps, 'YData', press , 'AlphaData', r1)
hold on
imagesc(r2*2,'XData',temps, 'YData', press , 'AlphaData', r2) %r2 scaled to get different color
colorbar 
plot(temps,press.^2+4)
plot(temps+50,(press-10).^3+4)
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