two variables one equation 3D plot

2021 11 24
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更新时间：2021 12 1
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Dear,
I have two input vector matrices as variables alf and gam:
alf = [0, 0.03, 0.1, 0.5, 1, 1.5];
gam = [0, 0.03, 0.1, 0.5, 1, 1.5];
Then I have some complicated steps resulting in one value for each possible combination of the two variables alf and gam.
For example alf=0.03 and gam=1 gives one answer. And alf=0.5 and gam=0 gives an other answer etc.
How can I plot this as a 3D plot with a surface with alf and gam as X and Y axes and the outcome Z axis.
if I try:
[gamM, alfM]=meshgrid(gam,alf);
surf(gamM,alfM,log10(T))
it gives me the error saying:
Error using surf (line 71)
Z must be a matrix, not a scalar or vector.
kind regards Nickel

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Dyuman Joshi
Dyuman Joshi 2021-11-25
编辑：Dyuman Joshi 2021-11-25
You might be storing T as row/column vector. Change it into a matrix.
Since you mentioned that you get a unique output for each gam and alf, then your T should have 36 elements. Convert it into a 6x6 matrix and try again.
Nickel Blankevoort
Nickel Blankevoort 2021-11-25
Dear Dyuman Joshi,
That is correct I get 36 individual elements for T.
But how do I convert that into a 6x6 matrix?
I run two For loops simultaneously for alf and gam, calculating T.
Kind regards Nickel
Dyuman Joshi
Dyuman Joshi 2021-11-25
for i=1:numel(alf)
for j=1:numel(gam)
T(i,j)= alf(i)*gam(j) %this is just an exmample, use your existing formula
end
end
Nickel Blankevoort
Nickel Blankevoort 2021-11-25
clc;clear
eL=0;
eR=0;
gammaL=-2;
gammaR=-2;
aL=-0.1;
aR=-0.1;
E=linspace(-0,0.0001,1);
kL=acos((eL-E)/(2*gammaL
kR=acos((eR-E)/(2*gammaR));
h=6.582119514*10^-16;
N = 3;
for alf = [0, 0.03, 0.1, 0.5, 1, 1.5];
for gam = [0, 0.03, 0.1, 0.5, 1, 1.5];
H = diag(gam.*ones(1,N-1),-1);
if N>2
H = diag(gam.*ones(1,N-1),-1)+diag(alf.*ones(1,N-2),-2);
else
H = diag(gam.*ones(1,N-1),-1);
end
H = H+H';
a=1;
b=N;
n=1;
g=(((E(n))*eye(length(H))-H))^-1;
gaa=g(a,a);
gbb=g(b,b);
gab=g(a,b);
gba=g(b,a);
vL=(2*gammaL*sin(kL(n)))/h;
vR=(2*gammaR*sin(kR(n)))/h;
gL=(exp(i*kL(n)))/(-gammaL);
gR=(exp(i*kR(n)))/(-gammaR);
sL=aL.^2*gL;
sR=aR.^2*gR;
d=1+sL*gaa+sR*gbb+sR*sL*(gaa*gbb-gab*gba);
t=i*h*sqrt(vL)*aL*gL*(gba/d)*gR*aR*sqrt(vR);
T(:,n)=[abs(t^2)]; %I would like to store the value of this T for every iteration
end
end
Nickel Blankevoort
Nickel Blankevoort 2021-11-25
编辑：Nickel Blankevoort 2021-11-25
Dear Dyuman,
thank you for the quick responses. I have included my code now for more clearity.
I try to store the values for T for every iteration.
Nickel
Dyuman Joshi
Dyuman Joshi 2021-11-25
I can't see your code? Or did you mean, that you have included what I wrote in your code?
Nickel Blankevoort
Nickel Blankevoort 2021-11-25
Can you see my code now in the attachement?
Nickel

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 采纳的回答

Dyuman Joshi
Dyuman Joshi 2021-11-25
Ran in:

1 个投票

Ran in:
I have modified your code -
clc;clear
eL=0;
eR=0;
gammaL=-2;
gammaR=-2;
aL=-0.1;
aR=-0.1;
E=linspace(-0,0.0001,1);
kL=acos((eL-E)/(2*gammaL));
kR=acos((eR-E)/(2*gammaR));
h=6.582119514*10^-16;
N = 3;
alf = [0, 0.03, 0.1, 0.5, 1, 1.5];
gam = [0, 0.03, 0.1, 0.5, 1, 1.5];
for i=1:6
for j=1:6
H = diag(gam(i).*ones(1,N-1),-1);
if N>2
H = diag(gam(i).*ones(1,N-1),-1)+diag(alf(i).*ones(1,N-2),-2);
else
H = diag(gam(i).*ones(1,N-1),-1);
end
H = H+H';
a=1;
b=N;
n=1;
g=(((E(n))*eye(length(H))-H))^-1;
gaa=g(a,a);
gbb=g(b,b);
gab=g(a,b);
gba=g(b,a);
vL=(2*gammaL*sin(kL(n)))/h;
vR=(2*gammaR*sin(kR(n)))/h;
gL=(exp(i*kL(n)))/(-gammaL);
gR=(exp(i*kR(n)))/(-gammaR);
sL=aL.^2*gL;
sR=aR.^2*gR;
d=1+sL*gaa+sR*gbb+sR*sL*(gaa*gbb-gab*gba);
t=i*h*sqrt(vL)*aL*gL*(gba/d)*gR*aR*sqrt(vR);
T(i,j)=[abs(t^2)]; %I would like to store the value of this T for every iteration
end
end
[gamM, alfM]=meshgrid(alf,alf);
surf(gamM,alfM,log10(T))

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Nickel Blankevoort
Nickel Blankevoort 2021-12-1
thanks a lot for the help, much appriciated!
Nickel Blankevoort
Nickel Blankevoort 2021-12-1
I didn't get the graphs I was expecting to get. Turned out you used i for the for loop too hahah, and in my equations I use i as imaginary... took me a couple of days to figure that out:)
But all happy now!
kind regards and big thanks again

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