How to extract the data (y-axis) for a given value ( x-value)?

In this IDA_Plot_CLUSTER_UPDATED.mat file, I'm able to plot the (Figure B) upto certain points. But I want to get the exact pattern of that part i.e. in each curve (figure B) after the end point it will be extended upto 0.08 in a constant pattern. In this same plot, I want to get the y-values of corresponding to certain value of x.

Note : Limit y-values

PGA_Scale = [0.1:0.1:5]; 
figure(21) % to plot figure B
 for tt = 1:60
  plot(MIDR(tt,:),PGA_EQ(tt,1)*PGA_Scale,'-*r','linewidth',0.5);hold on;
 end
 xlabel('Maximum Storey Drift Ratio (MSDR)')
 ylabel('IM (PGA)')     
 title('Incremental Dynamic Analysis (IDAs)for GMSetAll')
 set(gcf,'position',[ 146 378 858 779])
 set(findall(gcf,'-property','Fontsize'),'Fontsize',12)
 print('DT2100','-dpng','-r300');

Figure A

Figure B

 Desire_Limit_Collapse = 0.01; % values to be calculated from the graph corresponding this Desire_Limit_Collapse
for ii= 1:60
    IM_Collapse_find(ii)= interp1(MIDR(ii,:),PGA_EQ(ii,1)*PGA_Scale,Desire_Limit_Collapse);
end

Answer 1

[KSSV]

load('IDA_Plot_CLUSTER_UPDATED.mat') 
PGA_Scale = [0.1:0.1:5];
figure(1) % to plot figure B
% for tt = 1:60
%     plot(MIDR(tt,:),PGA_EQ(tt,1)*PGA_Scale,'-*r','linewidth',0.5);hold on;
% end
plot(MIDR',PGA_EQ'.*PGA_Scale','-*r','linewidth',0.5);
xlabel('Maximum Storey Drift Ratio (MSDR)')
ylabel('IM (PGA)')
title('Incremental Dynamic Analysis (IDAs)for GMSetAll')
set(findall(gcf,'-property','Fontsize'),'Fontsize',12)
print('DT2100','-dpng','-r300');

% Extend the plot 
figure(2)
xi = linspace(0,0.08,100) ; 
 for tt = 1:60
     yi = interp1(MIDR(tt,:),PGA_EQ(tt,1)*PGA_Scale,xi,'nearest','extrap') ; 
     plot(xi,yi,'-*r','linewidth',0.5);hold on;
end

[Sumit Saha]

@KSSV thanks. In this plot, for two or three curves smooth transition is possible?

[KSSV]

What do you mean by smooth transition? It is an extrapolation so cannot be trusted..

[Sumit Saha]

@KSSV yeah I know it's extrapolation. I'm just asking if there is a possiblity of making smooth transition i.e. no kink will be there in this plot.

[Sumit Saha]

@KSSV How to extract y data from this for certain x values?

[KSSV]

Use interp1.

If (x,y) is your data and you seek value at xi..

yi = interp1(x,y,xi)

[Sumit Saha]

@KSSV I want to interpolate data from the extended plot Kindly help me. In figure A, the way it had been shown.

[KSSV]

For extended plot too use interp1 with extrapolation on. This already I have shown/ given in the answer.