MATLAB: How to make a smooth graph

Hi, I have this data with me.

   P_load = [0,8000,10000,11000,20000,25000,25000,21000,30000,20000,12000,45000, 12000,45000,23300,12000,15000,17000,20000,16000,12200,1000,2000,100];% Watts

so how can I make it smoother?. I nearly damage my brain now.

Help appreciated.

Best Answer

   P_load = [0,8000,10000,11000,20000,25000,25000,21000,30000,20000,12000,45000, 12000,45000,23300,12000,15000,17000,20000,16000,12200,1000,2000,100];% Watts
   x=1:numel(P_load)
   xx=linspace(1,numel(x),1000)
   yy=interp1(x,P_load,xx,'spline')
   plot(x,P_load,'or',xx,yy,'-m')

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The problem is that you test for equivalence of floating point values. This is bound to cause errors, as has been discussed hundreds of times on this forum:

https://www.mathworks.com/matlabcentral/answers/57444-faq-why-is-0-3-0-2-0-1-not-equal-to-zero

https://www.mathworks.com/matlabcentral/answers/350303-why-0-6-is-not-equal-to-0-2-3

http://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html

etc., etc.

The solution is to use ismembertol, or compare the absolute difference against some tolerance value:

idx = false(size(NA2,1),1);
tol = 0.0001;
for k = 1:size(CapacityOut,1)
   idx = idx | abs(NA2(:,1)-CapacityOut(k))<tol;
end
out = NA2(idx,:);

giving:

>> out
out =
   0.00000   0.98000   1.00000   0.02000  -3.10000   1.00000   1.00000
   1.10000   0.98000   0.05910   0.02000  -2.00000   1.00000   0.07790
   2.00000   0.98000   0.03000   0.02000  -1.10000   1.00000   0.04940
   3.10000   0.98000   0.00000   0.02000  -0.00000   1.00000   0.02000
   4.20000   0.98000   0.00000   0.02000   1.10000   0.05910   0.00120
   5.10000   0.98000   0.00000   0.02000   2.00000   0.00000   0.00000
   6.20000   0.98000   0.00000   0.02000   3.10000   0.00000   0.00000
>>

MATLAB: How to label smooth spline graph

P_load = [0,8000,10000,11000,20000,25000,25000,21000,30000,20000,12000,45000,12000,45000,23300,12000,15000,17000,20000,16000,12200,1000,2000,100];% Watts


x=1:numel(P_load)
 xx=linspace(1,numel(x),1000)
   yy=interp1(x,P_load,xx,'pchip')
   plot(xx,yy,'-*g')
   P_gen = ones(1,24).*29000; % Watts
P_lowerlimit = ones(1,24).*10000; % Watts
hold on 
 xx=linspace(1,numel(x),1000)
   yy=interp1(x,P_gen,xx,'spline')
   plot(xx,yy,'-og','linewidth', 2)
   xx=linspace(1,numel(x),1000)
   yy=interp1(x,P_lowerlimit,xx,'spline')
   plot(xx,yy,'-b','linewidth', 2)
grid
xlim([1,24])
xlabel('Time (hours)')
ylabel('Power (Watts)')
hold on
Pnet1 = [];
Pbat1 = [];
Pnet2 = [];
Pbat2 = [];
for h = 1:24
    Pnet1(h) = P_gen(h) - P_load(h);
    Pnet2(h) = P_lowerlimit(h) - P_load(h);
    if Pnet1(h) > 0
        Pbat1(h) = 0;
    else
        Pbat1(h) = P_load(h) - P_gen(h);
    end 
    if Pnet2(h) < 0
        Pbat2(h) = 0;
    else
        Pbat2(h) = [P_gen(h) - P_load(h)]/3;
    end
end
xx=linspace(1,numel(x),1000)
   yy=interp1(x,Pbat1,xx,'spline')
   plot(xx,yy,'-y','linewidth', 3)
   xx=linspace(1,numel(x),1000)
   yy=interp1(x,Pbat2,xx,'spline')
   plot(xx,yy,'-r','linewidth', 3)
   legend('Load','Generator','Lower limit','Battery energy(Discharge)','Battery energy(Charge)'

Best Answer

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