fixed points in the plots

Hi,

I have a program that includes a graph of functions in 3D

I need to fix points on the drawing (show the location of the points on the drawing),

I used

hold on ;
plot (A(1),B(2.1),G(3.021),'r*')
plot (A(0.0001),B(3),G(3.21),'r*')
plot (A(3.654),B(3.1),G(2.15),'r*')

But an error appeared to me...

Error in POINTS (line 45)

plot (A(1),B(2.1),G(3.021),'r*')

if any Prof. can help me ...thanks alot

Answer 1

[Walter Roberson]

syms A B G

A, B, and G are created as scalar symbols

f = matlabFunction(sum1m2, 'vars', [A, B, G]);  
g = matlabFunction(sum3m4, 'vars', [A, B, G]);  
h = matlabFunction(sum5m6, 'vars', [A, B, G]);  

f, g, and h are created as numeric functions of three inputs.

plot (A(1),B(2.1),G(3.021),'r*')
plot (A(0.0001),B(3),G(3.21),'r*')
plot (A(3.654),B(3.1),G(2.15),'r*')

You try to index scalar A at 1, which works, giving you back the scalar symbol A .

You try to index scalar B at 2.1, which fails, because you cannot index at non-integers... and if you could do that, you would be indexing past the end of the scalar.

You try to index scalar G at 3.021, which fails, non integer, past the end of the scalar. Is it possible that function g was intended? But function g needs three parameters, not one.

I suspect what you want is

plot ((1),(2.1),(3.021),'r*')
plot ((0.0001),(3),(3.21),'r*')
plot ((3.654),(3.1),(2.15),'r*')

[hasan s]

Thanks Prof. Walter for the valuable answer... yes I want these points..I write it but also not appear in the graph

[hasan s]

I write the points as integer, but also not appear in the graph..

is imposible fixed points in graph in matlab???

[Walter Roberson]

It works for me. If I take your code and remove the

plot (A(1),B(2.1),G(3.021),'r*')
plot (A(0.0001),B(3),G(3.21),'r*')
plot (A(3.654),B(3.1),G(2.15),'r*')

which we already know to be wrong, and if we put in

plot3(1,2,3,'r*')

then you can see a red star in the graph.

You have "hold on" in effect, and your xlim, ylim, and zlim are all [0 4], so if you were to try to draw at points outside that range, then they would not be in view. For example if you wanted to plot at 4.1 3.1 2.1 then it would be off the screen. If that happens you can use

xlim auto; ylim auto; zlim auto

[hasan s]

realy appear in your matlab ... why not appear in my matlab ???

please where you put

plot ((1),(2.1),(3.021),'r*')

plot ((0.0001),(3),(3.21),'r*')

plot ((3.654),(3.1),(2.15),'r*')

I put it in the end of program , and I take the same file in the interval [0,4].please , if you can ..attach the file that appear the 3 points

I try

plot3(1,2,3,'r*')

and appear * without graph of functions

[Walter Roberson]

NumPoints = 50;
tic
digits(16);
syms A B G
N = 100;
Q1 = rand(10,N);
Q = vpa(reshape(Q1,1,[])); 
sum1=0;sum2=0;sum3=0;sum4=0;sum5=0;sum6=0;
for j=1:1000
    sum1=sum1+1/(A+(G*B*((Q(j))^(G-1))));
    sum2=sum2+(Q(j));
    sum3=sum3+(G*((Q(j))^(G-1)))/(A+(G*B*((Q(j))^(G-1))));
    sum4=sum4+(Q(j))^(G);
    sum5=sum5+(((G*log(Q(j)))*((Q(j))^(G-1)))+((Q(j))^(G-1)))/(A+(B*G*((Q(j))^(G-1))));
    sum6=sum6+((Q(j))^(G))*log(Q(j));
    
end
sum1m2 = vpa(sum1 - sum2);
sum3m4 = vpa(sum3 - sum4);
sum5m6 = vpa(B*sum5-B*sum6);
f = matlabFunction(sum1m2, 'vars', [A, B, G]);  
g = matlabFunction(sum3m4, 'vars', [A, B, G]);  
h = matlabFunction(sum5m6, 'vars', [A, B, G]);  
[Ag, Bg, Gg] = meshgrid(linspace(0, 4,NumPoints));
Fgrid = f(Ag,Bg,Gg);    
Ggrid = g(Ag,Bg,Gg);    
Hgrid = h(Ag,Bg,Gg);    
grids = {Fgrid, Ggrid, Hgrid};
gridnames = {'f', 'g', 'h'};
ngrid = length(grids);
cmap = parula(ngrid);
view(3);
patches = gobjects(1,ngrid);
surfaces = cell(ngrid, 1);
for K = 1 : ngrid
  surfaces{K} = isosurface(Ag, Bg, Gg, grids{K}, 0);
  patches(K) = patch(surfaces{K}, 'facecolor', cmap(K,:), 'edgecolor','none','FaceAlpha', 0.5, 'displayname', gridnames{K});
end
xlabel('A');
ylabel('B');
zlabel('G');
legend show

hold on ;
plot3((1),(2.1),(3.021),'r*')
plot3((0.0001),(3),(3.21),'r*')
plot3((3.654),(3.1),(2.15),'r*')
hold off
toc

[hasan s]

Now the points appear ...

Thank you very very much prof. Walter

please ...Why did the point name not appear with * , as

A 1

B 2.1

G 3.021

[Walter Roberson]

You did not ask for that.

points = [
    1, 2.1, 3.021;
    0.0001, 3, 3.21;
    3.654, 3.1, 2.15;
    ]
scatter3(points(:,1), points(:,2), points(:,3), 'r*');
for K = 1 : size(points,1)
   text(points(K,1), points(K,2), points(K,3), sprintf('A=%g B=%g G=%g', points(K,:)));
end

[hasan s]

Sorry, I thought it appears without other commands...

thank you very very much Prof. Walter

[Walter Roberson]

There are also datatips(), but datatips() automatically move to the closest data point, which I did not think you would want to do.

[hasan s]

Thanks prof. Walter for this valuable information ... Yes, right now, I just need to hold the points