Plotting 3 function using mesh command

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qudsia Bashir
qudsia Bashir il 10 Ott 2019
I have to plot 3 functions in matlab using mesh command but donot know how to do it please anyone help me?
  2 Commenti
Rik
Rik il 10 Ott 2019
What is the full text of your homework assignment and what have you tried to find out so far?
qudsia Bashir
qudsia Bashir il 10 Ott 2019
i solved an equation using 3 different method and now i want to plot the results obtained from these three methods.the function is of form u(x,y)

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Risposte (1)

Alexandra McClernon Ownbey
The best way to plot using mesh is to create three 2-D matrices with the same sizes.
x = 0:.1:1;
y = 0:.5:10;
[xq,yq] = meshgrid(x,y);
z = (xq.^2-yq.^2);
figure()
mesh(x,y,z)
Although 'x' and 'y' are different sizes, meshgrid creates a 2-D grid for xq and yq with the m rows and n columns where m equals the length of y and n equals the length of x.
I find the easiest way to think of it is this way:
a 3-D plot needs values for each x, y, and z position. 'xq' is the x coordinates for each point. 'yq' is the y coordinates for each point, and 'z' is the z-coordinates for each respective point. So you create a 2-D grid and give each point some height 'z'.
You do not need to use meshgrid to create your initial 2D matrices, but I find it works well for most cases.
  4 Commenti
qudsia Bashir
qudsia Bashir il 12 Ott 2019
i am using the code given below but its giving error that dimmension must agree i have cross check the dimmensions are the same of both functions donot know y this is happening syms x t
for K=1:20
D(1,K)=0 ;
end
for K=1:19
for h=0:19
A(K+1,h+1)=(pi).^(K+2*h);
B(K+1,h+1)=sind(((K+2*h)*180)/2)
D(K+1,h+1)=A(K+1,h+1)*B(K+1,h+1)/(factorial(K)*factorial(h));
end
end
s=0;
for i=1:18
for j=1:18
x=0.2:0.2:0.8;
s=s+D(i,j).*x.^(i-1).*t.^(j-1);
end
end
t=0:0.1:0.5;
sia=subs(s,t);
sia1=eval(subs(s,t));
t=0:0.1:0.5;x=(0.2:0.2:0.8)';
exact1 = bsxfun(@times,sin(pi*x),exp(-(pi)^2*t));
B = reshape(exact1',[],1);
exact=B';
errordtm=abs(exact-sia1);
dtmmatrix = vec2mat(sia1,6);
mesh(x,t,exact1,'edgecolor', 'b');
hold on
mesh(x,t,dtmmatrix,'edgecolor', 'r');
legend({'Numerical','Exact'})
hold off
Alexandra McClernon Ownbey
Modificato: Alexandra McClernon Ownbey il 13 Ott 2019
the length of your vector 'x' is 4, the length of your vector 't' is 6. just fix these dimensions to match. I suggest using linspace for t using the length of vector x.
I also would suggest initializing D using zeros.
D = zeros(20,1);

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