how do i calculate a 3d graph in this case?

Question

Cristina Anna Rossi 2022-10-23

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1833278-how-do-i-calculate-a-3d-graph-in-this-case

评论： Cristina Anna Rossi 2022-10-23

I am trying to draw a graph using the following formula, however i have two vectors instead of a matrices and while the values get calculated, I cannot plot them. I want to plot the graph as pi and pp change.

The code actually calculates the results for all the values, then says there is an error in line 33 without explaining what it is.

Thanks to anyone in advance.

q_wheat=240;
q_iron=12;
q_pig=18;
wheat_totale=450;
q_wheat2=120;
q_iron2=8;
q_pig2=12;
iron_totale=21;
q_wheat3=120;
q_iron3=6;
q_pig3=30;
pig_totale=60;
pw=1;
pi=0.1:0.1:40;
pp=0.1:0.1:40;
for i=1:length(pi)
    for j=1:length(pp)
    
    cost_w(i,j)=q_wheat*pw+(q_iron*pi(i,j))+(q_pig*pp(i,j))
    cost_i(i,j)=q_wheat2*pw+(q_iron2*pi(i,j))+(q_pig2*pp(i,j))
    cost_p(i,j)=q_wheat3*pw+(q_iron3*pi(i,j))+(q_pig3*pp(i,j))
    rev_wheat(i,j)=wheat_totale*pw;
    rev_iron(i,j)=iron_totale*pi(i,j);
    rev_pig(i,j)=pig_totale*pp(i,j)
    prof_iron(i,j)=rev_iron(i,j)-cost_i(i,j);
    prof_wheat(i,j)=rev_wheat(i,j)-cost_w(i,j);
    prof_pig(i,j)=rev_pig(i,j)-cost_p(i,j)
    riron(i,j)=(rev_iron(i,j)/cost_i(i,j))-1
    rwheat(i,j)=(rev_wheat(i,j)/cost_w(i,j))-1
    rpig(i,j)=(rev_pig(i,j)/cost_p(i,j))-1
    end
end
figure(1), plot(pi,riron,pi,rwheat,pi,rpig)

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Answer 1

Image Analyst 2022-10-23

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Not exactly sure what you want since you removed all your comments in the code, which I'm sure you put it (like all good programmers do), but this is what I got. Perhaps it's what you intended, perhaps not.

q_wheat = 240;

q_iron = 12;

q_pig = 18;

wheat_totale = 450;

q_wheat2 = 120;

q_iron2 = 8;

q_pig2 = 12;

iron_totale = 21;

q_wheat3 = 120;

q_iron3 = 6;

q_pig3 = 30;

pig_totale = 60;

pw = 1;

pk = 0.1:0.1:40;

pp = 0.1:0.1:40;

for i = 1:length(pk)

for j = 1:length(pp)

cost_w(i,j) = q_wheat*pw + (q_iron*pk(i)) + (q_pig*pp(j));

cost_i(i,j) = q_wheat2*pw + (q_iron2*pk(i)) + (q_pig2*pp(j));

cost_p(i,j) = q_wheat3*pw + (q_iron3*pk(i)) + (q_pig3*pp(j));

rev_wheat(i,j) = wheat_totale*pw;

rev_iron(i,j) = iron_totale*pk(i);

rev_pig(i,j) = pig_totale*pp(j);

prof_iron(i,j) = rev_iron(i,j)-cost_i(i,j);

prof_wheat(i,j) = rev_wheat(i,j)-cost_w(i,j);

prof_pig(i,j) = rev_pig(i,j)-cost_p(i,j);

riron(i,j) = (rev_iron(i,j)/cost_i(i,j))-1;

rwheat(i,j) = (rev_wheat(i,j)/cost_w(i,j))-1;

rpig(i,j) = (rev_pig(i,j)/cost_p(i,j))-1;

end

plot(pk,riron(i, :), 'r-') % Draw iron with a red curve for this i

hold on

plot(pk,rwheat(i, :), 'g-') % Draw wheat with a green curve for this i

plot(pk,rpig(i, :), 'b-') % Draw pig with a blue curve for this i

end

xlabel('pk')

ylabel('iron, wheat, or pig')

% Draw line along x axis

yline(0, 'LineWidth',2);

grid on;

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Cristina Anna Rossi 2022-10-23

Oh thank you! Yes this is what I needed, thank you so much!

I did remove all of my comments because they felt silly, but I will remember to keep them for future questions! I tend to panic a bit using matlab, this has helped me a lot, though, so thank you!

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